题目描述
给定一个仅包含数字 2-9 的字符串,返回所有它能表示的字母组合。答案可以按 任意顺序 返回。
给出数字到字母的映射如下(与电话按键相同)。注意 1 不对应任何字母。
样例
示例 1:
输入:digits = "23"
输出:["ad","ae","af","bd","be","bf","cd","ce","cf"]
示例 2:
输入:digits = ""
输出:[]
示例 3:
输入:digits = "2"
输出:["a","b","c"]
提示:
0 <= digits.length <= 4
digits[i] 是范围 [‘2’, ‘9’] 的一个数字。
(循环搜索)
C++ 代码
class Solution {
public:
string chars[8] = {"abc", "def", "ghi", "jkl", "mno", "pqrs", "tuv", "wxyz"};
vector<string> letterCombinations(string digits) {
if (digits.empty()) return vector<string> ();
vector<string> state(1, "");
for (auto u : digits)
{
vector<string> now;
for (auto c : chars[u - '2'])
{
for (auto s : state)
now.push_back(s + c);
}
state = now;
}
return state;
}
};