[剑指offer]二叉树中和为某一值的路径

题目描述

输入一颗二叉树的根节点和一个整数，打印出二叉树中结点值的和为输入整数的所有路径。路径定义为从树的根结点开始往下一直到叶结点所经过的结点形成一条路径。(注意: 在返回值的list中，数组长度大的数组靠前)

 

 

题目链接：

https://www.nowcoder.com/practice/b736e784e3e34731af99065031301bca?tpId=13&tqId=11177&rp=2&ru=/ta/coding-interviews&qru=/ta/coding-interviews/question-ranking

 

 

package com.sunshine.OFFER66_SECOND;

public class TreeNode {
    int val;
    TreeNode left;
    TreeNode right;

    TreeNode(int x) {
        val = x;
    }
}

 

 

package com.sunshine.OFFER66_SECOND;

import org.junit.Test;

import java.util.ArrayList;

public class A24_FindPath {


    @Test
    public void test() {
        TreeNode n1 = new TreeNode(1);
        TreeNode n2 = new TreeNode(2);
        TreeNode n3 = new TreeNode(3);
        TreeNode n4 = new TreeNode(6);
        TreeNode n5 = new TreeNode(5);
        TreeNode n7 = new TreeNode(1);
        n1.left = n2;
        n1.right = n3;
        n2.left = n4;
        n2.right = n5;
        n5.right = n7;

        ArrayList<ArrayList<Integer>> arrayLists = FindPath(n1, 9);
        arrayLists.forEach(a -> {
            a.forEach(b -> System.out.print(b + " ->"));
            System.out.println();
        });
    }


    ArrayList<ArrayList<Integer>> ans = new ArrayList<>();

    public ArrayList<ArrayList<Integer>> FindPath(TreeNode root, int target) {
        if(root==null){
            return ans;
        }
        FindAnswers(root, target, new ArrayList<>());
        ans.sort((ArrayList<Integer> a, ArrayList<Integer> b) -> a.size() >= b.size() ? -1 : 1);
        return ans;
    }

    public void FindAnswers(TreeNode cur, int sum, ArrayList<Integer> path) {
        int count = sum - cur.val;
        path.add(cur.val);
        if (count == 0 ) {
            if(cur.right == null && cur.left == null) {
                ArrayList<Integer> onePath = new ArrayList<>(path);
                ans.add(onePath);
                return;
            }else{
                return;
            }
        }else if(count < 0){
            return;
        }
        if(null != cur.left){
            FindAnswers(cur.left, count, path);
            path.remove(path.size() - 1);
        }
        if(null != cur.right) {
            FindAnswers(cur.right, count, path);
            path.remove(path.size() - 1);
        }
    }


}