LeetCode之Sum of Left Leaves

1、题目

Find the sum of all left leaves in a given binary tree.

Example:

    3   / \  9  20    /  \   15   7There are two left leaves in the binary tree, with values 9 and 15 respectively. Return 24.

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2、代码实现

/** * Definition for a binary tree node. * public class TreeNode { *     int val; *     TreeNode left; *     TreeNode right; *     TreeNode(int x) { val = x; } * } */public class Solution {    public int sumOfLeftLeaves(TreeNode head) {        if (head == null) return 0;int left = 0, right = 0;if (head.left != null && head.left.left == null && head.left.right == null) {left = head.left.val;} else {left = sumOfLeftLeaves(head.left);}right = sumOfLeftLeaves(head.right);return left + right;    }}