LeetCode Path Sum II

来源：互联网发布：瓦格纳马拉知乎编辑：程序博客网时间：2024/05/16 05:34
题目描述：https://oj.leetcode.com/problems/path-sum-ii/
给定一个二叉树，一个sum，找出所有从根结点到叶节点的路径，路径上的节点和为sum。DFS 可解，不多说。
package Path_Sum_II;import java.util.*;public class Solution { class TreeNode { int val; TreeNode left; TreeNode right; TreeNode(int x) { val = x; }}public  void dfs(TreeNode root,int sum,List<List<Integer>>ans,List<Integer>list){if(root.left==null&&root.right==null){                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          int sum1 =0;for(Integer i:list){sum1+=i;}if(sum1==sum)ans.add(new LinkedList<Integer>(list));return;}if(root.left != null){list.add(root.left.val);dfs(root.left,sum,ans,list);list.remove(list.size()-1);}if(root.right != null){list.add(root.right.val);dfs(root.right,sum,ans,list);list.remove(list.size()-1);}}    public  List<List<Integer>> pathSum(TreeNode root, int sum) {        List<List<Integer>> ans = new LinkedList<List<Integer>>();        if(root!=null){        List<Integer> list = new LinkedList<Integer>();        list.add(root.val);        dfs(root,sum,ans,list);        }        return ans;    }    // for test    public  TreeNode construct(int[] nodes){    TreeNode[] treenodes = new TreeNode[nodes.length];    treenodes[0] = new TreeNode(nodes[0]);    for(int i=1;i<nodes.length;i++){    if(nodes[i] != -1){    treenodes[i]=new TreeNode(nodes[i]);    if(i%2==1)    treenodes[i/2].left=treenodes[i];    if(i%2==0)    treenodes[i/2-1].right=treenodes[i];    }    }    return treenodes[0];    }public static void main(String[] args) {int[] nums = new int[]{5,4,8,11,-1,13,4,7,2,-1,-1,-1,-1,5,1};TreeNode root = new Solution().construct(nums);List<List<Integer>> ans = new Solution().pathSum(root,22);for(List<Integer> list :ans){for(Integer i : list){System.out.print(i+" ");}System.out.println("");}}}
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