LeetCode Path Sum II

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("");
}
}

}