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doubifeifeidoubifeifei
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第一周作业格式变更
1 parent 41f138a commit 136db8c

12 files changed

Lines changed: 472 additions & 0 deletions

‎Week_01/id_77/leetcode_153_077.java‎

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class Solution {
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public int findMin(int[] nums) {
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int left = 0,right = nums.length-1,end = nums.length-1,mid;
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if(end < 0){
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return -1;
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}else if(end == 0){
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return nums[0];
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}
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if(nums[0]<nums[end]){
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return nums[0];
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}
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int maxIndex = -1;
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while(left <= right){
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mid = left + ((right - left) >> 1);
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if(nums[mid] > nums[mid+1]){
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maxIndex = mid;
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break;
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}else if(nums[mid] < nums[0]){
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right = mid -1;
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}else{
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left = mid +1;
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}
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}
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return nums[maxIndex + 1];
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}
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}

‎Week_01/id_77/leetcode_20_077.java‎

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class Solution {
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public boolean isValid(String s) {
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Stack<Character> stack = new Stack<Character>();
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if(s.length() == 0){
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return true;
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}
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boolean flag = true;
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char ch;
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for(int i=0;i<s.length();i++){
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ch = s.charAt(i);
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try {
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if (ch == ')') {
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if ('('==stack.pop()) {
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continue;
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} else {
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return false;
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}
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} else if (ch==']') {
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if ('['==stack.pop()) {
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continue;
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} else {
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return false;
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}
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} else if (ch =='}') {
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if ('{'==stack.pop()) {
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continue;
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} else {
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return false;
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}
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}else{
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stack.push(ch);
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}
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} catch (Exception e) {
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return false;
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}
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}
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if(stack.size()>0){
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return false;
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}else {
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return flag;
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}
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}
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}

‎Week_01/id_77/leetcode_21_077.java‎

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/**
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* Definition for singly-linked list.
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* public class ListNode {
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* int val;
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* ListNode next;
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* ListNode(int x) { val = x; }
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* }
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*/
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class Solution {
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public ListNode mergeTwoLists(ListNode l1, ListNode l2) {
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ListNode p1 = l1;
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ListNode p2 = l2;
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if(l1==null){
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return l2;
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}else if(l2==null){
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return l1;
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}
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ListNode listNew ;
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if(p1.val<p2.val){
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listNew = new ListNode(p1.val);
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p1 = p1.next;
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}else{
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listNew = new ListNode(p2.val);
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p2 = p2.next;
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}
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ListNode p=listNew;
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while(p1!=null && p2!=null){
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if(p1.val<p2.val){
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p.next = new ListNode(p1.val);
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p1 = p1.next;
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}else{
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p.next = new ListNode(p2.val);
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p2 = p2.next;
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}
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p = p.next;
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}
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if(p1==null){
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p.next = p2;
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}else{
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p.next = p1;
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}
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return listNew;
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}
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}

‎Week_01/id_77/leetcode_24_077.java‎

Lines changed: 45 additions & 0 deletions
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/**
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* Definition for singly-linked list.
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* public class ListNode {
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* int val;
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* ListNode next;
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* ListNode(int x) { val = x; }
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* }
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*/
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class Solution {
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public ListNode swapPairs(ListNode head) {
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if(head == null || head.next == null){
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return head;
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}
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ListNode slowPointer = head;
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ListNode fastPointer = head.next;
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ListNode p=fastPointer.next;
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fastPointer.next = slowPointer;
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slowPointer.next =p;
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if(p == null){
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return fastPointer;
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}
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head = fastPointer;
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ListNode headPointer = fastPointer.next;
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slowPointer = p;
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fastPointer = p.next;
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while(slowPointer != null && fastPointer !=null){
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p=fastPointer.next;
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fastPointer.next = slowPointer;
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slowPointer.next =p;
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headPointer.next = fastPointer;
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headPointer = fastPointer.next;
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slowPointer = p;
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if(p!=null){
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fastPointer = p.next;
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}else{
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fastPointer= null;
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}
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}
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return head;
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}
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}

‎Week_01/id_77/leetcode_25_077 .java‎

Lines changed: 57 additions & 0 deletions
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/**
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* Definition for singly-linked list.
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* public class ListNode {
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* int val;
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* ListNode next;
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* ListNode(int x) { val = x; }
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* }
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*/
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class Solution {
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public ListNode reverseKGroup(ListNode head, int k) {
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if(head == null){
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return null;
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}
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//记录头节点
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ListNode headPointer = head;
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//记录尾节点
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ListNode tailPointer = head;
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//记录节点个数
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int n = 0;
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while(tailPointer != null){
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n++;
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if(n == k){
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//k以后的节点递归处理
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ListNode tmpTail = reverseKGroup(tailPointer.next,k);
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//反转前k个节点 并链接尾节点
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reverseK(headPointer,k).next = tmpTail;
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break;
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}
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tailPointer = tailPointer.next;
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}
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if(n < k){
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//不足k个节点 直接返回头节点
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return headPointer;
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}else{
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//有k个节点 返回反转后的头节点 即原来的尾节点
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return tailPointer;
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}
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}
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public ListNode reverseK(ListNode head, int k){
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if(k == 1){
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return head;
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}
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ListNode headNew = reverseK(head.next,k-1);
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headNew.next = head;
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head.next = null;
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return head;
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}
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}

‎Week_01/id_77/leetcode_33_077 .java‎

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class Solution {
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public int search(int[] nums, int target) {
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int left = 0,right = nums.length-1,end = nums.length-1,mid;
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if(end < 0){
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return -1;
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}else if(end == 0){
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return nums[0] == target ? 0 : -1;
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}
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if(nums[0]<nums[end]){
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return binarySearch(nums,target,0 ,end);
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}
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int maxIndex = -1;
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//查找最大值索引
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while(left <= right){
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mid = left + ((right - left) >> 1);
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if(nums[mid] > nums[mid+1]){
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maxIndex = mid;
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break;
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}else if(nums[mid] < nums[0]){
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right = mid -1;
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}else{
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left = mid +1;
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}
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}
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//比较最大值 进行区间二分查找
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if(target < nums[0]){
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return binarySearch(nums,target,maxIndex+1 ,end) ;
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}else{
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return binarySearch(nums,target,0 ,maxIndex) ;
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}
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}
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public int binarySearch(int[] nums,int target,int left ,int right){
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if(left>right){
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return -1;
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}
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int mid = left + ((right - left) >> 1);
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if(nums[mid] > target){
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return binarySearch(nums,target,left,mid-1);
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}else if(nums[mid] < target){
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return binarySearch(nums,target,mid + 1,right);
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}else{
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return mid;
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}
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}
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}

‎Week_01/id_77/leetcode_33_077.java‎

Lines changed: 51 additions & 0 deletions
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class Solution {
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public int search(int[] nums, int target) {
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int left = 0,right = nums.length-1,end = nums.length-1,mid;
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if(end < 0){
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return -1;
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}else if(end == 0){
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return nums[0] == target ? 0 : -1;
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}
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if(nums[0]<nums[end]){
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return binarySearch(nums,target,0 ,end);
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}
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int maxIndex = -1;
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//查找最大值索引
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while(left <= right){
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mid = left + ((right - left) >> 1);
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if(nums[mid] > nums[mid+1]){
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maxIndex = mid;
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break;
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}else if(nums[mid] < nums[0]){
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right = mid -1;
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}else{
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left = mid +1;
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}
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}
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//比较最大值 进行区间二分查找
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if(target < nums[0]){
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return binarySearch(nums,target,maxIndex+1 ,end) ;
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}else{
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return binarySearch(nums,target,0 ,maxIndex) ;
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}
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}
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public int binarySearch(int[] nums,int target,int left ,int right){
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if(left>right){
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return -1;
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}
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int mid = left + ((right - left) >> 1);
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if(nums[mid] > target){
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return binarySearch(nums,target,left,mid-1);
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}else if(nums[mid] < target){
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return binarySearch(nums,target,mid + 1,right);
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}else{
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return mid;
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}
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}
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}

‎Week_01/id_77/leetcode_496_077.java‎

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class Solution {
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// 默认初始值
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private static final Integer VALUED_EFAULT = Integer.valueOf(-1);
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public int[] nextGreaterElement(int[] nums1, int[] nums2) {
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Stack<Integer> stack = new Stack<Integer>();
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//利用哨兵来去除判空
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stack.push(Integer.MAX_VALUE);
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Map<Integer,Integer> map = new HashMap<Integer,Integer>();
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int[] arr = new int[nums1.length];
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for(Integer node:nums2){
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while( node > stack.peek()){
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map.put(stack.pop(),node);
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}
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stack.push(node);
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}
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for(int i = 0;i < nums1.length;i++){
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//获取为空时添加默认值
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arr[i] = map.getOrDefault(nums1[i],VALUED_EFAULT);
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}
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return arr;
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}
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}

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