LeetCode 017 Letter Combinations of a Phone Number

求手机上的数字所对应的字母之间的组合可能。用递归来做比较简单。

class Solution {
public:
    int yy[10]={0,0,3,3,3,3,3,4,3,4};//对应每个数字所拥有的字母的个数
    char str_ss[10000];
    vector<string> letterCombinations(string digits) {
        vector<string>res;
        if(digits.size()==0)return res;
        get_ans(0,digits,res);
        return res;
    }
public:
    void get_ans(int index,string ans,vector<string>& res){
        if(index>=ans.size()){res.push_back(str_ss);return ;}
        int ww=ans[index]-'2';
        int get_number=0;
        while(ww){
           	if(ww==6)get_number+=4;
    	   <span style="white-space:pre">	</span> else get_number+=3;
           <span style="white-space:pre">	</span> ww--;
        }
        for(int ii=get_number;ii<get_number+yy[ans[index]-'0'];ii++){
            str_ss[index]='a'+ii;
            get_ans(index+1,ans,res);
        }
    }
};