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   7

There 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;
    }
}