回溯(递归)
class Solution {
vector<string> ans;
map<int, string> m;
public:
vector<string> letterCombinations(string digits) {
m[2] = "abc";
m[3] = "def";
m[4] = "ghi";
m[5] = "jkl";
m[6] = "mno";
m[7] = "pqrs";
m[8] = "tuv";
m[9] = "wxyz";
string res;
parse(digits, res);
return ans;
}
void parse(string digits, string res) {
if(digits.size() == 0 && res != "") {
ans.push_back(res);
}
int d = digits[0] - '0';
for(int i = 0; i < m[d].size(); i++) {
string temp = res;
temp += m[d][i];
parse(digits.substr(1, digits.size() - 1), temp);
}
}
};
题目链接:https://leetcode-cn.com/problems/letter-combinations-of-a-phone-number/submissions/