Leetcode-标签为Tree 112. Path Sum

原题

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.

代码分析

求解根到叶子的路径是否存在一条等于指定值。注意要计算到叶子。

代码实现

        public bool HasPathSum(TreeNode root, int sum)        {            if (root == null)                return false;            if (root.val == sum && root.isLeaf()) //判断是否加到了叶子                return true;            //求以root为根的路径val和等于sum的            if (HasPathSum(root.left, sum - root.val) == true)                return true;            return HasPathSum(root.right, sum - root.val);        }        public bool isLeaf()        {            return left == null && right == null;        }