Create 1457-pseudo-palindromic-paths-in-a-binary-tree.js

javascript/1457-pseudo-palindromic-paths-in-a-binary-tree.js

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+/**
+ * 
+ * Definition for a binary tree node.
+ * function TreeNode(val, left, right) {
+ *     this.val = (val===undefined ? 0 : val)
+ *     this.left = (left===undefined ? null : left)
+ *     this.right = (right===undefined ? null : right)
+ * }
+ */
+/**
+ * DFS | Hashing | Backtraking | tree-traversal
+ * Time O(n) | Space O(n)
+ * https://leetcode.com/problems/pseudo-palindromic-paths-in-a-binary-tree/
+ * @param {TreeNode} root
+ * @return {number}
+ */
+var pseudoPalindromicPaths  = function(root) {
+
+    const addNum = (num, hashSet) => {
+        hashSet[num] = (hashSet[num] + 1) || 1;
+    }
+
+    const removeNum = (num, hashSet) => {
+        hashSet[num] = hashSet[num] - 1;
+        if (hashSet[num] === 0) delete hashSet[num];
+    }
+
+    const isPalindrome = (hashSet) => {
+
+        let oddOccurances = 0;
+
+        for (const key in hashSet) {
+            if (hashSet[key] % 2) oddOccurances++;
+        }
+
+        return oddOccurances < 2;
+    }
+
+    const dfs = (node, hashSet) => {
+        if (!node.left && !node.right && isPalindrome(hashSet)) return 1;
+        if (!node.left && !node.right) return 0;
+
+        let total = 0;
+        if (node.left) {
+            addNum(node.left.val, hashSet);
+            total += dfs(node.left, hashSet);
+            removeNum(node.left.val, hashSet);
+        } 
+
+        if (node.right) {
+            addNum(node.right.val, hashSet);
+            total += dfs(node.right, hashSet);
+            removeNum(node.right.val, hashSet);
+        }
+
+        return total;
+    }   
+
+    return dfs(root, {[root.val]: 1} \);
+
+};