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| class Solution {
public:
vector<string> letterCombinations(string digits) {
if (digits.empty()) return {};
doit(digits, {});
return ret;
}
private:
void doit(string digits, string const& str) {
if (digits.size() == 0) {
ret.emplace_back(str);
return;
}
vector<char>& charset = dict[int(digits[0]) - 48];
for (int i = 0; i < charset.size(); ++i) {
doit({digits.begin() + 1, digits.end()}, str + charset[i]);
}
}
map<int, vector<char>> dict = {
{2, {'a', 'b', 'c'}},
{3, {'d', 'e', 'f'}},
{4, {'g', 'h', 'i'}},
{5, {'j', 'k', 'l'}},
{6, {'m', 'n', 'o'}},
{7, {'p', 'q', 'r', 's'}},
{8, {'t', 'u', 'v'}},
{9, {'w', 'x', 'y', 'z'}}
};
vector<string> ret;
};
|
