LeetCode-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.
这道题看起来十分弱小,吃掉它
class Solution { public: vector<string> letterCombinations(string digits) { // Start typing your C/C++ solution below // DO NOT write int main() function vector<string> ret; if(digits.length()==0){ ret.push_back(""); return ret; } map<char,string> m; m['2']="abc"; m['3']="def"; m['4']="ghi"; m['5']="jkl"; m['6']="mno"; m['7']="pqrs"; m['8']="tuv"; m['9']="wxyz"; m['0']=" "; m['*']="+"; vector<int> ptr; ptr.resize(digits.length()); for(int i=0;i<ptr.size();i++)ptr[i]=0; int i=0; string rs; for(;;){ string s=m[digits[i]]; if(ptr[i]==s.length()){ i--; if(i<0)break; rs.resize(i); } else{ rs+=s[ptr[i]]; ptr[i]++; i++; if(i>=digits.length()){ ret.push_back(rs); i--; rs.resize(i); } else{ ptr[i]=0; } } } return ret; } };