binary tree - bfs recu O(n) O(n) + iter O(n) O(n)

Author: lukeist

leetcode-102-binaryTreeLevelOrderTraversal.js

@@ -0,0 +1,48 @@
+/**
+ * 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)
+ * }
+ */
+/**
+ * @param {TreeNode} root
+ * @return {number[][]}
+ */
+
+// p: root of bi tree;
+// r: array
+
+// bfs recursive
+var levelOrder = function (root) {
+  if (!root) return [];
+  const result = [];
+
+  const lo = (root, level, result) => {
+    if (!root) return;
+    if (!result[level]) result[level] = [];
+    result[level].push(root.val);
+    lo(root.left, level + 1, result);
+    lo(root.right, level + 1, result);
+  };
+  lo(root, 0, result);
+  return result;
+};
+
+// bfs iterative
+// var levelOrder = function(root) {
+//     if (!root) return [];
+//     const queue = [[root, 0]];
+//     const result = [];
+//     while (queue.length > 0) {
+//         const [c, level] = queue.shift();
+//         if (!result[level]) result[level] = [];
+//         result[level].push(c.val);
+
+//         c.left && queue.push([c.left, level + 1]);
+//         c.right && queue.push([c.right, level + 1]);
+//     }
+
+//     return result;
+// };