leetcode-algorithms-17 Letter Combinations of a Phone Number
leetcode-algorithms-17 Letter Combinations of a Phone Number
Given a string containing digits from 2-9 inclusive, return all possible letter combinations that the number could represent.
A mapping of digit to letters (just like on the telephone buttons) is given below. Note that 1 does not map to any letters.
Example:
Input: "23"
Output: ["ad", "ae", "af", "bd", "be", "bf", "cd", "ce", "cf"].
Note:
Although the above answer is in lexicographical order, your answer could be in any order you want.
解法
通过数字对应的字符串,循环.
class Solution
{
public:
vector<string> letterCombinations(string digits)
{
std::vector<std::string> result;
if (digits.empty()) return result;
result = {""};
std::vector<std::string> v = {"", "", "abc", "def", "ghi", "jkl", "mno", "pqrs", "tuv", "wxyz"};
for(int i = 0 ; i < digits.size(); ++i)
{
int num = digits[i] - '0';
if(num < 0 || num > 9)
break;
std::string cand = v[num];
if(cand.empty())
continue;
std::vector<std::string> tmp = result;
result.clear();
for(int j = 0; j < tmp.size(); ++j)
{
for(int k = 0; k < cand.size(); ++k)
result.push_back(tmp[j] + cand[k]);
}
}
return result;
}
};
