112. Path Sum

題目原文

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.

Note: A leaf is a node with no children.

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.

解題思路

程式解答

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution 
{
public:
    bool hasPathSum(TreeNode* root, int sum) 
    {
        if (!root)
            return false;

        sum -= root->val;
        if (!root->left && !root->right)
        {
            if (sum == 0)
                return true;
            else
                return false;
        }
        return hasPathSum(root->left, sum) || hasPathSum(root->right, sum);
    }
};