问题一：电话号码的字母组合
解题思路
代码
class Solution {
vector<string> ans;
string strs[10] = {"","","abc","def","ghi","jkl","mno","pqrs","tuv","wxyz"};
public:
vector<string> letterCombinations(string digits) {
if(digits.length() == 0) return ans;
dfs(digits,0,"");
return ans;
}
void dfs(string digits, int index, string combine){
if(index == digits.length())
{
ans.push_back(combine);
return ;
}
string s = strs[digits[index] - '0'];
for(int i = 0; i < s.length(); i++)
{
combine.push_back(s[i]);
dfs(digits, index + 1, combine);
combine.pop_back();
}
}
};
