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Week 2 homework
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‎Week_01/id_26/Leetcode_236_26.java‎

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package com.fanlu.leetcode.binarytree;
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// Source : https://leetcode.com/problems/lowest-common-ancestor-of-a-binary-tree/
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// Id : 236
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// Author : Fanlu Hai
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// Date : 2018-04-24
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// Other : lowest common ancestor (LCA): The lowest common ancestor is defined between two nodes p and q
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// as the lowest node in T that has both p and q as descendants
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// (where we allow a node to be a descendant of itself).
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// Tips :
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import java.util.LinkedList;
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import java.util.Queue;
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/**
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* Definition for a binary tree node.
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* public class TreeNode {
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* int val;
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* TreeNode left;
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* TreeNode right;
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* TreeNode(int x) { val = x; }
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* }
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*/
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public class LowestCommonAncestorOfABinaryTree {
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private TreeNode ans;
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// This answer is copied from leetcode submission analysis sample
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// 100.00% (20% faster than original) 44.21%
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public TreeNode lowestCommonAncestor(TreeNode root, TreeNode p, TreeNode q) {
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this.recurse(root, p, q);
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return this.ans;
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}
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private boolean recurse(TreeNode node, TreeNode p, TreeNode q) {
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if (node == null) {
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return false;
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}
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// rec left
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// it's very hard for me to write below code even though it's nothing hard.
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int left = this.recurse(node.left, p, q) ? 1 : 0;
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int right = this.recurse(node.right, p, q) ? 1 : 0;
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int mid = (node == p) || (node == q) ? 1 : 0;
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// this is better than comparing objects
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if (mid + left + right >= 2) {
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this.ans = node;
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}
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return (mid + left + right > 0);
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}
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//65.83% 40.60%
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// this is fast enough to my understanding, but there are more elegant and faster ways to do the same steps
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public TreeNode lowestCommonAncestorOriginal(TreeNode root, TreeNode p, TreeNode q) {
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if (null == root || root == p || root == q)
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return root;
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TreeNode left = lowestCommonAncestorOriginal(root.left, p, q);
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TreeNode right = lowestCommonAncestorOriginal(root.right, p, q);
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if (null != left && null != right) {
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return root;
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} else if (null == right) {
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return left;
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} else {
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// null == left
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return right;
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}
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//return left == null ? right : right == null ? left : root;
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}
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/**
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* below are some no very successfull attampts
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*/
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Queue<TreeNode> pNodeList = new LinkedList<>();
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Queue<TreeNode> qNodeList = new LinkedList<>();
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//! Time Limit Exceeded
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public TreeNode lowestCommonAncestorTooSlow(TreeNode root, TreeNode p, TreeNode q) {
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TreeNode result = root;
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dfsNode(root, p, q, new LinkedList<TreeNode>());
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while (!pNodeList.isEmpty()) {
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TreeNode tmp = pNodeList.poll();
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// System.out.println(tmp);
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if (tmp != qNodeList.poll()) {
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break;
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}
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result = tmp;
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}
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return result;
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}
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public void dfsNode(TreeNode treeNode, TreeNode p, TreeNode q, Queue<TreeNode> queue) {
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if (null == treeNode)
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return;
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Queue<TreeNode> tmpQueue = new LinkedList<>();
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tmpQueue.addAll(queue);
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tmpQueue.add(treeNode);
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if (treeNode.val == p.val) {
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pNodeList = tmpQueue;
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}
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if (treeNode.val == q.val) {
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qNodeList = tmpQueue;
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}
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dfsNode(treeNode.left, p, q, tmpQueue);
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dfsNode(treeNode.right, p, q, tmpQueue);
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}
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Queue<Integer> pList = new LinkedList<>();
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Queue<Integer> qList = new LinkedList<>();
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// implemented the int version
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public int lowestCommonAncestorReturnInt(TreeNode root, TreeNode p, TreeNode q) {
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int result = root.val;
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dfsValue(root, p.val, q.val, new LinkedList<Integer>());
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while (!pList.isEmpty()) {
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int tmp = pList.poll();
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// System.out.println(tmp);
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if (tmp != qList.poll()) {
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break;
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}
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result = tmp;
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}
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return result;
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}
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public void dfsValue(TreeNode treeNode, int p, int q, Queue<Integer> queue) {
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if (null == treeNode)
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return;
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Queue<Integer> tmpQueue = new LinkedList<>();
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tmpQueue.addAll(queue);
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tmpQueue.add(treeNode.val);
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if (treeNode.val == p) {
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pList = tmpQueue;
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}
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if (treeNode.val == q) {
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qList = tmpQueue;
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}
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dfsValue(treeNode.left, p, q, tmpQueue);
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dfsValue(treeNode.right, p, q, tmpQueue);
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}
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public static void main(String[] args) {
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TreeNode treeNode1 = new TreeNode(1);
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TreeNode treeNode2 = new TreeNode(2);
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TreeNode treeNode3 = new TreeNode(3);
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TreeNode treeNode4 = new TreeNode(4);
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TreeNode treeNode5 = new TreeNode(5);
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TreeNode treeNode6 = new TreeNode(6);
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TreeNode treeNode7 = new TreeNode(7);
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treeNode1.left = treeNode2;
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treeNode2.left = treeNode4;
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treeNode2.right = treeNode5;
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treeNode5.right = treeNode3;
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treeNode3.left = treeNode6;
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treeNode3.right = treeNode7;
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LowestCommonAncestorOfABinaryTree lowestCommonAncestorOfABinaryTree = new LowestCommonAncestorOfABinaryTree();
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lowestCommonAncestorOfABinaryTree.dfsValue(treeNode1, 7, 6, new LinkedList<Integer>());
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for (int i : lowestCommonAncestorOfABinaryTree.pList) {
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System.out.print(i + "*");
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}
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System.out.println();
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for (int i : lowestCommonAncestorOfABinaryTree.qList) {
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System.out.print(i + "-");
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}
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System.out.println();
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System.out.println("result: " + lowestCommonAncestorOfABinaryTree.lowestCommonAncestorReturnInt(treeNode1, treeNode7, treeNode6));
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}
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}

‎Week_01/id_26/Leetcode_242_26.java‎

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package com.fanlu.leetcode.hashtable;
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// Source : https://leetcode.com/problems/valid-anagram/
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// Id : 242
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// Author : Fanlu Hai
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// Date : 2018-04-22
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// Other : anagram noun. a word, phrase, or name formed by rearranging the letters of another, such as cinema, formed from iceman.
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// Tips : 1.Use int[] with ascii as hash table; 2.use 'for i certain numbers' instead of 'for reach'.
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public class ValidAnagram {
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//38.34% 70.24%
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public boolean isAnagramSlow(String s, String t) {
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if (null == s || null == t)
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return false;
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if (s.length() != t.length())
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return false;
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int[] letters = new int[26];
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for (int i = 0; i < s.length(); i++) {
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int tmpS = s.charAt(i) - 'a';
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int tmpT = t.charAt(i) - 'a';
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letters[tmpS]++;
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letters[tmpT]--;
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}
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for (int i = 0; i < 26; i++) {
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if (letters[i] != 0)
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return false;
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}
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return true;
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}
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// try to remove tmp variables to see if it runs faster
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// And it does
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// 72.38% 70.94%
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public boolean isAnagramFast(String s, String t) {
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if (null == s || null == t)
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return false;
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if (s.length() != t.length())
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return false;
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int[] letters = new int[26];
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for (int i = 0; i < s.length(); i++) {
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letters[s.charAt(i) - 'a']++;
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letters[t.charAt(i) - 'a']--;
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}
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for (int i : letters) {
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if (letters[i] != 0)
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return false;
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}
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return true;
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}
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// try to remove tmp variables to see if it runs faster
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// And it does
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// use for i instead of for reach, it becomes even faster
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// 90.46% 71.14%
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public boolean isAnagram(String s, String t) {
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if (null == s || null == t)
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return false;
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if (s.length() != t.length())
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return false;
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int[] letters = new int[26];
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for (int i = 0; i < s.length(); i++) {
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letters[s.charAt(i) - 'a']++;
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letters[t.charAt(i) - 'a']--;
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}
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for (int i = 0; i < 26; i++) {
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if (letters[i] != 0)
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return false;
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}
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return true;
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}
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public static void main(String[] args) {
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ValidAnagram validAnagram = new ValidAnagram();
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System.out.println(validAnagram.isAnagram("abcdefg", "abcdefg"));
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System.out.println(validAnagram.isAnagram("abcdefg", "abcdefgg"));
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System.out.println(validAnagram.isAnagram("abcdefg", "gbcdefa"));
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System.out.println(validAnagram.isAnagram("aaaaaaa", "aaaaaba"));
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System.out.println(validAnagram.isAnagram(null, null));
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}
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}

‎Week_01/id_26/Leetcode_609_26.java‎

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package com.fanlu.leetcode.hashtable;
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// Source : https://leetcode.com/problems/find-duplicate-file-in-system/
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// Id : 609
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// Author : Fanlu Hai
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// Date : 2018-04-23
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// Other :
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// Tips :
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import java.util.*;
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/**
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* Input:
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* ["root/a 1.txt(abcd) 2.txt(efgh)", "root/c 3.txt(abcd)", "root/c/d 4.txt(efgh)", "root 4.txt(efgh)"]
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* Output:
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* [["root/a/2.txt","root/c/d/4.txt","root/4.txt"],["root/a/1.txt","root/c/3.txt"]]
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*/
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public class FindDuplicateFileInSystem {
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Map<String, ArrayList<String>> map = new HashMap<>();
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//75.63% 20.59%
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public List<List<String>> findDuplicateOriginal(String[] paths) {
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for (String s : paths) {
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getContentMapFromPath(s);
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}
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//! below codes cause concurrent modification exception, use iterator instead
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// for(String key : map.keySet()){
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// if (map.get(key).size()==1)
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// map.remove(key);
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// }
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Iterator<Map.Entry<String, ArrayList<String>>> iterator = map.entrySet().iterator();
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while (iterator.hasNext()) {
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Map.Entry<String, ArrayList<String>> entry = iterator.next();
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if (entry.getValue().size() == 1) {
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iterator.remove();
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}
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}
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return new ArrayList<List<String>>(map.values());
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}
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public void getContentMapFromPath(String path) {
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String[] tmp = path.split(" ");
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String prefix = tmp[0] + "/";
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for (int i = 1; i < tmp.length; i++) {
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String[] foo = tmp[i].split("\\(");
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// use content value as key, an arrayList of paths as value.
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String key = foo[1].substring(0, foo[1].length() - 1);
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ArrayList<String> value = map.getOrDefault(key, new ArrayList<String>());
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value.add(prefix + foo[0]);
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map.put(key, value);
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}
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}
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//63.86% 76.47%
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public List<List<String>> findDuplicate(String[] paths) {
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Map<String, Set<String>> map = new HashMap<>();
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for (String path : paths) {
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String[] tmp = path.split(" ");
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for (int i = 1; i < tmp.length; i++) {
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String[] foo = tmp[i].split("\\(");
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// use content value as key, an arrayList of paths as value.
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String key = foo[1].substring(0, foo[1].length() - 1);
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Set<String> value = map.getOrDefault(key, new HashSet<String>());
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value.add(tmp[0] + "/" + foo[0]);
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map.put(key, value);
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}
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}
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List<List<String>> result = new ArrayList<List<String>>();
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for (Set<String> list : map.values()) {
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if (list.size() != 1)
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result.add(new ArrayList<>(list));
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}
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return result;
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}
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}

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