LeetCode-Easy刷题(26) Path Sum

Posted 2022-05-31 当以乐

Given a binary tree and a sum, determine if the tree has a root-to-leaf path such that adding up all the values along the path equals the given sum.

For example:
Given the below binary tree and   sum = 22,

              5
             / \\
            4   8
           /   / \\
          11  13  4
         /  \\      \\
        7    2      1

return true, as there exist a root-to-leaf path 5->4->11->2 which sum is 22.

判断是否存在从根节点到叶子节点的值相加结果为给定的值,存在返回true,否则false;

 //深度优先  维护要完成的剩余目标值
    public boolean hasPathSum(TreeNode root, int sum) 

        if(root ==null)//以最后空接点作为递归结束
            return false;
        
        //满足题意的结束条件
        if(root.left ==null && root.right ==null && root.val == sum)
            return true;
        
        return hasPathSum(root.left, sum - root.val) || hasPathSum(root.right, sum - root.val) ;