【LeetCode】 113. Path Sum II 路径总和 II(Medium)(JAVA)
题目地址: https://leetcode.com/problems/path-sum-ii/
题目描述:
Given a binary tree and a sum, find all root-to-leaf paths where each path’s sum equals the given sum.
Note: A leaf is a node with no children.
Example:
Given the below binary tree and sum = 22,
5
/ \
4 8
/ / \
11 13 4
/ \ / \
7 2 5 1
Return:
[
[5,4,11,2],
[5,8,4,5]
]
题目大意
给定一个二叉树和一个目标和,找到所有从根节点到叶子节点路径总和等于给定目标和的路径。
说明: 叶子节点是指没有子节点的节点。
解题方法
1、采用递归
2、加入列表之后,递归过后删除
/**
* Definition for a binary tree node.
* public class TreeNode {
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode(int x) { val = x; }
* }
*/
class Solution {
List<List<Integer>> res = new ArrayList<>();
public List<List<Integer>> pathSum(TreeNode root, int sum) {
if (root == null) return res;
pH(root, sum, new ArrayList<>());
return res;
}
public void pH(TreeNode root, int sum, List<Integer> list) {
if (root == null) return;
list.add(root.val);
sum -= root.val;
if (root.left == null && root.right == null) {
if (sum == 0) res.add(new ArrayList<>(list));
} else if (root.left == null) {
pH(root.right, sum, list);
}else if (root.right == null) {
pH(root.left, sum, list);
} else {
pH(root.right, sum, list);
pH(root.left, sum, list);
}
list.remove(list.size() - 1);
}
}
执行用时 : 2 ms, 在所有 Java 提交中击败了 65.44% 的用户
内存消耗 : 39.6 MB, 在所有 Java 提交中击败了 5.26% 的用户