Leetcode Problems 242, 290, 345, 383 Done.

omprashantjain · omprashantjain · commit a0a466caaede · 2024-04-19T11:33:50.000+05:30
diff --git a/3 Strings/242 Valid Anagram.java b/3 Strings/242 Valid Anagram.java
@@ -0,0 +1,24 @@
+import java.util.HashMap;
+
+class Solution {
+  public boolean isAnagram(String s, String t) {
+    if (s.length() != t.length()) {
+      return false;
+    }
+    HashMap<Character, Integer> countMap = new HashMap<>();
+    for (int i = 0 ; i < s.length(); i++) {
+      char sChar = s.charAt(i);
+      char tChar = t.charAt(i);
+
+      countMap.put(sChar, countMap.getOrDefault(sChar, 0) + 1);
+      countMap.put(tChar, countMap.getOrDefault(tChar, 0) - 1);
+    }
+
+    for (int value : countMap.values()) {
+      if (value != 0) {
+        return false;
+      }
+    }
+    return true;
+  }
+}
diff --git a/3 Strings/290 Word Pattern.java b/3 Strings/290 Word Pattern.java
@@ -0,0 +1,33 @@
+import java.util.HashMap;
+
+class Solution {
+  public boolean wordPattern(String pattern, String s) {
+    String[] words = s.split(" ");
+    if (pattern.length() != words.length) {
+      return false;
+    }
+    HashMap<Character, String> lToW = new HashMap<>();
+    HashMap<String, Character> wToL = new HashMap<>();
+    for (int i = 0 ; i < pattern.length(); i++) {
+      char letter = pattern.charAt(i);
+      String word = words[i];
+
+      if (lToW.containsKey(letter)) {
+        if (!lToW.get(letter).equals(word)) {
+          return false;
+        }
+      } else {
+        lToW.put(letter, word);
+      }
+
+      if (wToL.containsKey(word)) {
+        if (wToL.get(word) != letter) {
+          return false;
+        }
+      } else {
+        wToL.put(word, letter);
+      }  
+    }
+    return true;
+  }
+}
diff --git a/3 Strings/345 Reverse Vowels of a String.java b/3 Strings/345 Reverse Vowels of a String.java
@@ -0,0 +1,28 @@
+class Solution {
+  public String reverseVowels(String s) {
+    char[] letters = s.toCharArray();
+    int i = 0, j = s.length() - 1;
+
+    while (i < j) {
+      // increment till i reaches a vowel
+      while (i < j && !isVowel(letters[i])) i++;
+
+      // decrement till j reaches a vowel
+      while (i < j && !isVowel(letters[j])) j--;
+
+      if (i < j) {
+        char temp = letters[i];
+        letters[i] = letters[j];
+        letters[j] = temp;
+        i++;
+        j--;
+      }
+    }
+    return new String(letters);
+  }
+
+  private boolean isVowel(char c) {
+    final String VOWELS = "aeiouAEIOU";
+    return VOWELS.indexOf(c) != -1;
+  }
+}
diff --git a/3 Strings/383 Ransom Note.java b/3 Strings/383 Ransom Note.java
@@ -0,0 +1,19 @@
+class Solution {
+  public boolean canConstruct(String ransomNote, String magazine) {
+    int[] counts = new int[26];
+    for (char c : magazine.toCharArray()) {
+      int index = c - 'a';
+      counts[index]++;
+    }
+    for (char c : ransomNote.toCharArray()) {
+      int index = c - 'a';
+      counts[index]--;
+    }
+    for (int count: counts) {
+      if (count < 0) {
+        return false;
+      }
+    }
+    return true;
+  }
+}
