17 Letter Combinations of a Phone Number
/*
String[] mapping = new String[] {"0", "1", "abc", "def", "ghi", "jkl", "mno", "pqrs", "tuv", "wxyz"};
*/
class Solution {
public:
vector<string> letterCombinations(string digits) {
vector<string> ans;
if(digits.size() == 0) return ans;
string charmap[10] = {"0", "1", "abc", "def", "ghi", "jkl", "mno", "pqrs", "tuv", "wxyz"};
vector<string> temp;
ans.push_back("");
for(int i = 0; i<digits.size();i++)
{
//int num = atoi(digits[i]);
int num = digits[i]-'0';
string str = charmap[num];
for (char c:str)
{
for(string s :ans)
{
temp.push_back(s+c);
}
}
ans = temp;
temp.clear();
}
return ans;
}
};