LintCode: Binary Tree Paths

C++

/**
 * Definition of TreeNode:
 * class TreeNode {
 * public:
 *     int val;
 *     TreeNode *left, *right;
 *     TreeNode(int val) {
 *         this->val = val;
 *         this->left = this->right = NULL;
 *     }
 * }
 */
class Solution {
public:
    /**
     * @param root the root of the binary tree
     * @return all root-to-leaf paths
     */
    vector<string> binaryTreePaths(TreeNode* root) {
        // Write your code here
        vector<string> result;
        if (root == NULL) {
            return result;
        }
        string path="";
        binaryTreePathsCore(root, result, path);
        return result;
    }
    void binaryTreePathsCore(TreeNode* root, vector<string> &result, string path) {
        if (root == NULL) {
            return;
        }
        int i = root->val;
        char a[5];
        // itoa(i, a, 10);
        sprintf(a, "%d", i);
        if ("" == path) {
            path = a;
        } else {
            path = path + "->" + a;
        }
        if (root->left == NULL && root->right == NULL) {
            result.push_back(path);
            return;
        }
        if (root->left != NULL) {
            binaryTreePathsCore(root->left, result, path);
        }
        if (root->right != NULL) {
            binaryTreePathsCore(root->right, result, path);
        }
        
        
    }
};