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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
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原文地址：http://www.cnblogs.com/wuchanming/p/4126334.html
