Leetcode-Letter Combinations of a Phone Number

题目:

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.

 

采用dfs深度搜索.

 1 #include <iostream>

 2 #include <map>

 3 #include <vector>

 4 #include <string>

 5 

 6 class Solution{

 7 private:

 8        map<char,vector<char> > dict;

 9        vector<string> res;

10 public:

11          void createDict()

12        {

13             dict.clear();

14              dict['2'].push_back('a');

15             dict['2'].push_back('b');

16             dict['2'].push_back('c');

17             dict['3'].push_back('d');

18             dict['3'].push_back('e');

19             dict['3'].push_back('f');

20             dict['4'].push_back('g');

21             dict['4'].push_back('h');

22             dict['4'].push_back('i');

23             dict['5'].push_back('j');

24             dict['5'].push_back('k');

25             dict['5'].push_back('l');

26             dict['6'].push_back('m');

27             dict['6'].push_back('n');

28             dict['6'].push_back('o');

29             dict['7'].push_back('p');

30             dict['7'].push_back('q');

31             dict['7'].push_back('r');

32             dict['7'].push_back('s');

33             dict['8'].push_back('t');

34              dict['8'].push_back('u');

35              dict['8'].push_back('v');

36              dict['9'].push_back('w');

37             dict['9'].push_back('x');

38             dict['9'].push_back('y');

39             dict['9'].push_back('z');

40         }

41         

42         void dfs(int dep,int maxDep,string &s,string ans){

43               if(dep==maxDep){

44                   res.push_back(ans);

45                   return;

46               }

47               

48               for(int i=0;i<dict[s[dep]].size();i++){

49                   dfs(dep+1,maxDep,s,ans+dict[s[dep]][i]);

50               }

51         }

52     

53       vector<string> letterCombinations(string digits){

54              res.clear();

55              createDict();

56              dfs(0,digits.size(),digits,"");

57       }

58     

59 };