subject

Input the following node and an integer of a binary tree, and print out all paths in which the sum of node values in the binary tree is the input integer. Path is defined as a path from the root node of the tree to the node that the leaf node passes through. (Note: in the list of returned values, the array with large array length is first)

thinking

import java.util.ArrayList;
/**
public class TreeNode {
    int val = 0;
    TreeNode left = null;
    TreeNode right = null;

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

    }

}
*/
public class Solution {
    
    public ArrayList<ArrayList<Integer>> FindPath(TreeNode root,int target) {
        ArrayList<ArrayList<Integer>> ans = new ArrayList<ArrayList<Integer>>();
        if(root == null)
            return ans;
        
        ArrayList<Integer> list = new ArrayList<Integer>();
        Find(root, target, ans, list, 0);
        
        return ans;
    }
    
    public void Find(TreeNode root, int target,
                     ArrayList<ArrayList<Integer>> ans, ArrayList<Integer> list, int sum){
        if(root == null || sum+root.val > target)
            return ;
        sum += root.val;
        
        if(root.left == null && root.right == null){
            if(target == sum){
                list.add(root.val);
                ans.add(new ArrayList<Integer>(list));//Add the same list as list
                list.remove(list.size()-1);//Remove the newly added node for subsequent operations in other situations
            }
            return ;
        }
        
        list.add(root.val); //Cannot be placed before the previous if
        Find(root.left, target, ans, list, sum);
        Find(root.right, target, ans, list, sum);
        list.remove(list.size()-1);//Remove the newly added node for subsequent operations in other situations
    }
}

Linked list replication

import java.util.ArrayList;
import java.util.Collections;

public class Solution {
    public static void main(String[] args) {
    	System.out.println("The following operations on a single linked list do not affect the data of another linked list(Operations with comments)");
    	System.out.println("==================ArrayList<Integer> desc = new ArrayList<Integer>(src);===============================");
		ArrayList<Integer> a = new ArrayList<Integer>();
		a.add(4);
		a.add(5);
		a.add(65);
		for (Integer integer : a) {
			System.out.print(integer+" ");
		}
		System.out.println();
		
		ArrayList<Integer> b = new ArrayList<Integer>(a);
		for (Integer integer : b) {
			System.out.print(integer+" ");
		}
		System.out.println();
		System.out.println("Comparison:"+(a==b));
		
		//b.clear();
		a.set(0, 1000);
		//b.remove(2);
		for (Integer integer : a) {
			System.out.print(integer+" ");
		}
		System.out.println();
		
		for (Integer integer : b) {
			System.out.print(integer+" ");
		}
		System.out.println("\n====================Collections.copy(desc, src);=============================");
		
		ArrayList<Integer> c = new ArrayList<Integer>();
		c.add(54);
		c.add(65);
		c.add(87);
		Collections.copy(c, b);
		System.out.println("Comparison:"+(c==b));
		for (Integer integer : b) {
			System.out.print(integer+" ");
		}
		System.out.println();
		
		for (Integer integer : c) {
			System.out.print(integer+" ");
		}
		System.out.println();
		
		//b.clear();
		//c.set(0, 1000);
		b.remove(2);
		for (Integer integer : c) {
			System.out.print(integer+" ");
		}
		System.out.println();
		
		for (Integer integer : b) {
			System.out.print(integer+" ");
		}
	}
    
}

Operation result:

If there is any mistake or unreasonable place, please correct it~

Come on!!