题解 | #二叉树中和为某一值的路径(二)#

递归 回溯

/**
public class TreeNode {
    int val = 0;
    TreeNode left = null;
    TreeNode right = null;

    public TreeNode(int val) {
        this.val = val;

    }

}
*/
import java.util.*;
public class Solution {
    public ArrayList<ArrayList<Integer>> FindPath(TreeNode root,int expectNumber) {
        if(root == null){
            return new ArrayList<ArrayList<Integer>>() ;
        }
        Deque<Integer> deque = new LinkedList<Integer>();
        ArrayList<ArrayList<Integer>>  res = new ArrayList<ArrayList<Integer>>();
        dfs(root,expectNumber,res,deque);
        return res;
    }
    
    public  void dfs(TreeNode root,int target,ArrayList<ArrayList<Integer>> res,Deque<Integer> deque){
        if(root == null){
            return ;
        }
        deque.addLast(root.val);
        target -=root.val;
        if(root.left == null && root.right ==null && target == 0 ){
            ArrayList<Integer> arr = new ArrayList<Integer>(deque);
            res.add(arr);
        }
        dfs(root.left,target,res,deque);
        dfs(root.right,target,res,deque);
        deque.pollLast();
    }
}