Add Invert Binary Tree and Valid Anagram

Author: andrewbayd

src/com/andrewbayd/ValidAnagram.java

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+package com.andrewbayd;
+
+import java.util.HashMap;
+import java.util.Map;
+
+/*
+Given two strings s and t, return true if t is an anagram of s, and false otherwise.
+An Anagram is a word or phrase formed by rearranging the letters of a different word or phrase, typically using all the original letters exactly once.
+
+https://leetcode.com/problems/valid-anagram/
+ */
+
+public class ValidAnagram {
+
+    public static boolean isAnagram(String s, String t) {
+        Map<Character, Integer> map = new HashMap<>();
+
+        if (s.length() != t.length()) {
+            return false;
+        }
+
+        for (char c : s.toCharArray()) {
+            map.put(c, map.getOrDefault(c, 0) + 1);
+        }
+
+        for (char c : t.toCharArray()) {
+            if (map.containsKey(c)) {
+                map.put(c, map.get(c) - 1);
+            } else {
+                return false;
+            }
+        }
+        for (int i : map.values()) {
+            if (i != 0) return false;
+        }
+        return true;
+    }
+
+    public static void main(String[] args) {
+        System.out.println(isAnagram("anagram", "nagaram")); //-> true
+        System.out.println(isAnagram("rat", "car")); //-> false
+    }
+}

src/com/andrewbayd/invertBinaryTree/Solution.java

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+package com.andrewbayd.invertBinaryTree;
+
+/*
+Given the root of a binary tree, invert the tree, and return its root.
+
+https://leetcode.com/problems/invert-binary-tree/
+ */
+
+public class Solution {
+
+    public TreeNode invertTree(TreeNode root) {
+        invertRecursive(root);
+        return root;
+
+    }
+
+    private void invertRecursive(TreeNode root) {
+        if (root == null) {
+            return;
+        }
+        TreeNode temp = root.left;
+        root.left = root.right;
+        root.right = temp;
+        invertRecursive(root.left);
+        invertRecursive(root.right);
+    }
+}

src/com/andrewbayd/invertBinaryTree/TreeNode.java

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+package com.andrewbayd.invertBinaryTree;
+
+// Definition for a binary tree node.
+public class TreeNode {
+    int val;
+    TreeNode left;
+    TreeNode right;
+
+    TreeNode() {
+    }
+
+    TreeNode(int val) {
+        this.val = val;
+    }
+
+    TreeNode(int val, TreeNode left, TreeNode right) {
+        this.val = val;
+        this.left = left;
+        this.right = right;
+    }
+}