p404

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LeetCode p404 Sum of Left Leaves 题解

1.题目：

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

Example:

3

/ \
9 20
/ \
15 7

There are two left leaves in the binary tree, with values 9 and 15 respectively. Return 24.

题意：

输入一个二叉树，输出所有左节点的累加和。

2.解题思路:

这里的左节点指左右节点都为空的左节点。

3.代码

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/**
 * 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 root) {
        if (root == null)
			return 0;
		if (root.left == null)
			return sumOfLeftLeaves(root.right);
		if (root.left.left == null && root.left.right == null)
			return root.left.val + sumOfLeftLeaves(root.right);
		return sumOfLeftLeaves(root.left) + sumOfLeftLeaves(root.right);
    }
}

4.一些总结：