solve: binary tree level order traversal

Author: wogha95

binary-tree-level-order-traversal/wogha95.js

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+/**
+ * 1차
+ *
+ * TC: O(N)
+ * SC: O(N)
+ * N: total of nodes
+ */
+
+/**
+ * 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[][]}
+ */
+var levelOrder = function (root) {
+  const result = [];
+
+  const queue = [
+    {
+      level: 0,
+      current: root,
+    },
+  ];
+
+  while (queue.length > 0) {
+    const { level, current } = queue.shift();
+
+    if (!current) {
+      continue;
+    }
+
+    if (result[level]) {
+      result[level].push(current.val);
+    } else {
+      result[level] = [current.val];
+    }
+
+    if (current.left) {
+      queue.push({
+        level: level + 1,
+        current: current.left,
+      });
+    }
+
+    if (current.right) {
+      queue.push({
+        level: level + 1,
+        current: current.right,
+      });
+    }
+  }
+
+  return result;
+};