题解 | 二叉树中和为某一值的路径(一)

import java.util.*;

/*
 * public class TreeNode {
 *   int val = 0;
 *   TreeNode left = null;
 *   TreeNode right = null;
 *   public TreeNode(int val) {
 *     this.val = val;
 *   }
 * }
 */

public class Solution {
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     * 
     * @param root TreeNode类 
     * @param sum int整型 
     * @return bool布尔型
     */
    public boolean hasPathSum (TreeNode root, int sum) {
        // write code here
        if(root == null) return false;
        Stack<TreeNode> s1 = new Stack<>();
        Stack<Integer> s2 = new Stack<>();
        s1.push(root);
        s2.push(root.val);
        while(!s1.isEmpty()){
            TreeNode temp = s1.pop();
            int cur_sum = s2.pop();
            if(temp.left == null &&temp.right == null &&cur_sum == sum) return true;
            if(temp.left != null){
                s1.push(temp.left);
                s2.push(cur_sum+temp.left.val);
            }
            if(temp.right != null){
                s1.push(temp.right);
                s2.push(cur_sum+temp.right.val);
            }
        }
        return false;
    }
}

用的dfs 还不是很熟对这个方法