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.
class Solution { public: const vector<string> key = {"", "", "abc", "def", "ghi", "jkl", "mno", "pqrs", "tuv", "wxyz"}; vector<string> letterCombinations(string digits) { vector<string> result; if (digits.size() == 0) return result; string str(digits.size(), ' '); PushString(digits, 0, str, result); return result; } private: void PushString(string& digits, int k,string &str,vector<string>& result) { if (k == digits.size()) { cout << str.size() << endl; result.push_back(str); return; } for (int i = 0; i < key[digits[k]-'0'].size(); i++) { str[k] = key[digits[k]-'0'][i]; //因为每一个str的长度都等于digits的大小,所以str可以重用(完全覆盖) PushString(digits, k+1, str, result); } } };
leetcode | Letter Combinations of a Phone Number
原文地址:http://blog.csdn.net/quzhongxin/article/details/46134829