Create 1028-recover-a-tree-from-preorder-traversal.js

Solved 1028-recover-a-tree-from-preorder-traversal.js

Author: aadil42

Diff for: javascript/1028-recover-a-tree-from-preorder-traversal.js

@@ -0,0 +1,58 @@
+/**
+ * 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)
+ * }
+ */
+/**
+ * PreOrderTraversal | DFS | Tree
+ * Time O(n) | Space O(n)
+ * https://leetcode.com/problems/recover-a-tree-from-preorder-traversal
+ * @param {string} traversal
+ * @return {TreeNode}
+ */
+var recoverFromPreorder = function(traversal) {
+    let i = 0;
+    const preOrderArr = [];
+    const depthArr = [];
+
+    while (i < traversal.length) {
+
+        const start = i;
+        if (traversal[i] === "-") {
+            while (i < traversal.length && traversal[i] === "-") {
+                i++;
+            }
+            depthArr.push(i-start);
+            continue;
+        }
+
+        while (i < traversal.length && traversal[i] !== "-") {
+            i++;
+        }
+        preOrderArr.push(+traversal.slice(start, i));
+    }
+
+    let idx = 0;
+    const dfs = (node, depth) => {
+        
+        node.val = preOrderArr[idx];
+
+        if (depth < depthArr[idx]) {
+            node.left = new TreeNode();
+            idx++;
+            dfs(node.left, depth+1);
+        }
+        if (depth < depthArr[idx]) {
+            node.right = new TreeNode();
+            idx++;
+            dfs(node.right, depth+1);
+        }
+    }
+
+    const root = new TreeNode();
+    dfs(root, 0);
+    return root;
+};