剑指offer-二叉树中和为某一值的路径

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 {
    ArrayList<ArrayList<Integer>> paths =new ArrayList<>();
    public ArrayList<ArrayList<Integer>> FindPath(TreeNode root,int target) {
        findPath(root,target,0,new ArrayList<>());
        return paths;
    }
    
    public void findPath(TreeNode cur,int target,int sum,ArrayList<Integer> path){
        //剪枝，当前和已大于目标和时直接返回
        if(cur == null || sum >= target){
            return;
        }
        //走过该节点，所以添加到路径中，并加上该节点的值
        path.add(cur.val);
        sum+=cur.val;
        //判断是否是叶子节点，是则判断是否满足和，否则不做操作
        if(cur.left == null && cur.right == null){
            if(target == sum){
                ArrayList<Integer> tmp =new ArrayList<>();
                for(int i =0 ;i<path.size();i++){
                    tmp.add(path.get(i));
                }
                paths.add(tmp);
            }
        }
        //遍历左节点
        if(cur.left != null){
            findPath(cur.left,target,sum,path);
        }
        //遍历右节点
        if(cur.right != null){
            findPath(cur.right,target,sum,path);
        }
        //和减去该节点的值，路径上去掉该节点
        sum-=cur.val;
        path.remove(path.size()-1);
    }
}