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;
}
}
