LeetCode Letter Combinations of a Phone Number C++

#include <iostream>#include <vector>#include<algorithm>#include <queue>using namespace std;/************************************************************************//*Problem:Given a digit string, return all possible letter combinations that the number could represent.A mapping of digit to letters (just like on the telephone buttons) is given below.For example:    1       2       3            abc     edf    4       5       6    ghi     jkl     mno    7       8       9    pqrs    tuv     wxzy    Input:Digit string "23"    Output: ["ad", "ae", "af", "bd", "be", "bf", "cd", "ce", "cf"].Author  :   [e-mail]:   2017年8月5日  12:06:17*//************************************************************************/class Solution {public:    vector<string> letterCombinations(string digits)    {        vector<string>_result;        if (digits.size() < 1)            return _result;         //定义9个按钮        vector<string>_zinum = {"", "abc", "def", "ghi", "jkl", "mno", "pqrs", "tuv", "wxzy" };        int _size = digits.size();        _result.push_back("");        for (int i = 0; i < _size; i++)        {            int num = digits[i] - '1';            if (num <1 || num > 9)                continue;            std::string& _str = _zinum[num];            if (_str.empty())                continue;            std::vector<string > _tempresult;            for (int j = 0; j < _str.size(); ++j)            {                for (int k = 0; k<_result.size(); ++k)                {                    //按照顺序相加  双层for循环。。把每一个for的第一个字母 宇第二组字母都相加插入到新的容器里面                    //然后swap 交换。                    _tempresult.push_back(_result[k] + _str[j]);                }            }            _result.swap(_tempresult);        }        return _result;    }};void main(){    std::string _str = "2";    Solution s1;    vector<string>_nums;    _nums = s1.letterCombinations(_str);    std::cout << "" << endl;    system("pause");}