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Letter Combinations of a Phone Number

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.

Input:Digit string "23"Output: ["ad", "ae", "af", "bd", "be", "bf", "cd", "ce", "cf"].

Note:
Although the above answer is in lexicographical order, your answer could be in any order you want.

参考:http://www.cnblogs.com/TenosDoIt/p/3771254.html

与LeetCode:Subsets I II 类似

 

C++实现代码:

#include<iostream>#include<vector>#include<string>using namespace std;class Solution {public:    vector<string> letterCombinations(string digits) {        vector<string> ret(1,"");        if(digits.empty())            return ret;        string str[]={" ","","abc","def","ghi","jkl","mno","pqrs","tuv","wxyz"};        size_t i,j,k;        for(i=0;i<digits.size();i++)        {            string s=str[digits[i]-0];            vector<string> tmp=ret;            ret.clear();            for(j=0;j<tmp.size();j++)            {                for(k=0;k<s.size();k++)                    ret.push_back(tmp[j]+s[k]);            }        }        return ret;    }};int main(){    Solution s;    vector<string> result=s.letterCombinations(string("31"));    for(auto a:result)        cout<<a<<endl;}

 

Letter Combinations of a Phone Number