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https://gitlab.com/mfocko/LeetCode.git
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57 lines
1.5 KiB
C++
57 lines
1.5 KiB
C++
#include <array>
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#include <cassert>
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#include <string>
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#include <vector>
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struct Solution {
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std::vector<std::string> letterCombinations(const std::string &digits) {
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solver s(digits);
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s.solve();
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return s.combinations;
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}
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private:
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struct solver {
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const std::string &digits;
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std::vector<std::string> combinations;
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solver(const std::string &digits) : digits(digits) {}
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void solve() {
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std::string s;
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solve(s, 0);
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}
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private:
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std::array<std::string, 8> LETTERS{"abc", "def", "ghi", "jkl",
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"mno", "pqrs", "tuv", "wxyz"};
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void solve(std::string &s, int i) {
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if (i < 0 || i >= static_cast<int>(digits.size())) {
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if (!s.empty()) {
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combinations.emplace_back(s);
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}
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return;
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}
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for (char c : LETTERS[digits[i] - '2']) {
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s.push_back(c);
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solve(s, i + 1);
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s.pop_back();
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}
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}
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};
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};
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int main() {
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Solution s;
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assert((s.letterCombinations("23") ==
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std::vector<std::string>{"ad", "ae", "af", "bd", "be", "bf", "cd",
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"ce", "cf"}));
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assert((s.letterCombinations("") == std::vector<std::string>{}));
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assert(
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(s.letterCombinations("2") == std::vector<std::string>{"a", "b", "c"}));
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return 0;
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}
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