[LeetCode] Letter Combinations of a Phone Number

http://oj.leetcode.com/problems/letter-combinations-of-a-phone-number/

这道题是LeetCode上独立做出来的第一道题, dfs.

这道题一开始总wa, 后来发现是stl string用错了, 我初始化是这么写的 string str(10); 导致所有str都是长10, 估计LeetCode会做检查, 所以就wa了, 后来就采用了先push, 递归后pop的方法,ac了.

string str;
string arr[10] = {" ", "", "abc", "def", "ghi", "jkl", "mno", "pqrs", "tuv", "wxyz"};
class Solution {
public:
    vector<string> re;
    void dfs(string digits, int cur) {
        if (cur == digits.size()) {
            re.push_back(str);
        } else {
            int index = digits[cur] - '0';
            for (int i = 0; i < arr[index].size(); ++i) {
                str.push_back(arr[index][i]);
                dfs(digits, cur + 1);
                str.pop_back();
            }
        }
    }
    vector<string> letterCombinations(string digits) {
        re.clear();
        dfs(digits, 0);
        return re;
    }
};