Create 222. 完全二叉树的节点个数.js

Author: yinxin630

222. 完全二叉树的节点个数.js

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+/**
+ * Definition for a binary tree node.
+ * function TreeNode(val) {
+ *     this.val = val;
+ *     this.left = this.right = null;
+ * }
+ */
+/**
+ * @param {TreeNode} root
+ * @return {number}
+ */
+var countNodes = function(root) {
+  function dfs(node) {
+    if (!node) {
+      return 0;
+    }
+    return 1 + dfs(node.left) + dfs(node.right);
+  }
+  return dfs(root);
+};