本文主要是介绍LeetCode 17 Letter Combinations of a Phone Number，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！
题意：
给出数字串s，输出按照9键键盘输入s时可能的所有字符串。
思路：
没思路……直接模拟过程就得了……
写switch好看点……吧……
代码：
class Solution {
public:vector<string> letterCombinations(string digits) {vector<string> res;if(!digits.size()){return res;}res.push_back("");for(int i = 0; i < digits.size(); ++i){res = grow(res, digits[i]);}return res;}
private:vector<string> grow(vector<string> fath, char son){vector<string> res;switch(son){case '1':{res = fath;break;}case '2':{for(string s : fath){res.push_back(s + 'a');res.push_back(s + 'b');res.push_back(s + 'c');}break;}case '3':{for(string s : fath){res.push_back(s + 'd');res.push_back(s + 'e');res.push_back(s + 'f');}break;}case '4':{for(string s : fath){res.push_back(s + 'g');res.push_back(s + 'h');res.push_back(s + 'i');}break;}case '5':{for(string s : fath){res.push_back(s + 'j');res.push_back(s + 'k');res.push_back(s + 'l');}break;}case '6':{for(string s : fath){res.push_back(s + 'm');res.push_back(s + 'n');res.push_back(s + 'o');}break;}case '7':{for(string s : fath){res.push_back(s + 'p');res.push_back(s + 'q');res.push_back(s + 'r');res.push_back(s + 's');}break;}case '8':{for(string s : fath){res.push_back(s + 't');res.push_back(s + 'u');res.push_back(s + 'v');}break;}case '9':{for(string s : fath){res.push_back(s + 'w');res.push_back(s + 'x');res.push_back(s + 'y');res.push_back(s + 'z');}break;}case '0':{for(string s : fath){res.push_back(s + ' ');}break;}}return res;}
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