두 갈래 나무의 화합

1404 단어
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.
/**
 * Definition for binary tree
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    bool calBranchSum(TreeNode *root, int sum, int prevSum)
    {
        if (root == NULL)
        {
            return false;
        }

        prevSum += root->val;
        if (root->left == NULL && root->right == NULL)
        {
            if (prevSum == sum)
            {
                return true;
            }
            return false;
        }

        bool left = calBranchSum(root->left, sum, prevSum);
        if (left)
        {
            return true;
        }

        return calBranchSum(root->right, sum, prevSum);
    }

    bool hasPathSum(TreeNode *root, int sum) {
       return calBranchSum(root, sum, 0);
    }
};

좋은 웹페이지 즐겨찾기