Lstmxx的空间

404. 左叶子之和

计算给定二叉树的所有左叶子之和。

链接

/**
 * Definition for a binary tree node.
 * class TreeNode {
 *     val: number
 *     left: TreeNode | null
 *     right: TreeNode | null
 *     constructor(val?: number, left?: TreeNode | null, right?: TreeNode | null) {
 *         this.val = (val===undefined ? 0 : val)
 *         this.left = (left===undefined ? null : left)
 *         this.right = (right===undefined ? null : right)
 *     }
 * }
 */
let sum = 0

function sumOfLeftLeaves(root: TreeNode | null): number {
  sum = 0
  traverse(root)
  return sum
};

function traverse(root: TreeNode | null) {
  if (root === null) return
  const left = root.left
  if (left !== null && left.left === null && left.right === null) {
    sum += left.val
  }
  traverse(left)
  traverse(root.right)
}