题目介绍

题解

class Solution {
    public boolean hasPathSum(TreeNode root, int targetSum) {
        // 只在最开始的时候判断树是否为空
        if (root == null) {
            return false;
        }
        
        targetSum -= root.val;
        if (root.left == null && root.right == null) { // root 是叶子节点
            return targetSum == 0;
        }
        return hasPathSum(root.left, targetSum) || hasPathSum(root.right, targetSum);
    }
}