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 class Solution {
    /**
     * 
     * @param root TreeNode类 
     * @param sum int整型 
     * @return bool布尔型
     */
    public boolean hasPathSum (TreeNode root, int sum) {
        // write code here
        //下面的代码是自己写的用减法实现路径
        if(root == null){
            return false;
        }
        Stack<TreeNode> stack = new Stack<>();
        Stack<Integer> sums = new Stack<>();
        stack.push(root);
        sums.push(sum);
        while(!stack.isEmpty()){
            TreeNode cur = stack.pop();
            int cursum = sums.pop();
            if(cur.left == null && cur.right == null){
                if(cur.val == cursum){
                    return true;
                }
            }
            if(cur.right != null){
                sums.push(cursum - cur.val);
                stack.push(cur.right);
            }
            if(cur.left != null){
                sums.push(cursum - cur.val);
                stack.push(cur.left);
            }
        }
        return false;
    }
}