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0404_sum_of_left_leaves.java
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79 lines (63 loc) · 1.65 KB
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/*
* https://leetcode-cn.com/problems/sum-of-left-leaves/
计算给定二叉树的所有左叶子之和。
示例：
3
/ \
9 20
/ \
15 7
在这个二叉树中，有两个左叶子，分别是 9 和 15，所以返回 24
---------------------------------------------------------------------------
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.
*/
/**
* Definition for a binary tree node.
* public class TreeNode {
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode(int x) { val = x; }
* }
*/
class MySolution {
// 0 : 根节点
// 1 : 左叶子
// 2 : 右叶子
private int sum = 0;
public int sumOfLeftLeaves(TreeNode root) {
sumOfLeftLeaves(root, 0);
return sum;
}
private void sumOfLeftLeaves(TreeNode node, int side) {
if (node == null) return ;
if (node.left == null && node.right == null)
sum += side % 2 * node.val;
sumOfLeftLeaves(node.left, 1);
sumOfLeftLeaves(node.right, 2);
}
}
class Solution1 {
public int sumOfLeftLeaves(TreeNode root) {
int sum = 0;
if (root == null) {
return 0;
}
if(root.left != null){
if(root.left.left == null && root.left.right == null) {
sum += root.left.val;
} else {
sum += sumOfLeftLeaves(root.left);
}
}
sum += sumOfLeftLeaves(root.right);
return sum;
}
}