原題網址:https://leetcode.com/problems/sum-of-left-leaves/
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.
方法:遞歸,深度遍歷搜索。
/**
* 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) {
int sum = 0;
if (root == null) return sum;
if (root.left != null) {
if (root.left.left == null && root.left.right == null) {
sum += root.left.val;
} else {
sum += sumOfLeftLeaves(root.left);
}
}
if (root.right != null) {
sum += sumOfLeftLeaves(root.right);
}
return sum;
}
}