91 lines
3.3 KiB
C++
91 lines
3.3 KiB
C++
#include <iostream>
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#include <vector>
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#include <algorithm>
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#include <numeric>
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using namespace std;
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void log_vector(const vector<int>& vec, const string& prefix = "") {
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clog << prefix;
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for (const int i : vec) { clog << i << " "; }
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clog << endl;
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}
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vector<int> get_divisors(const int n) {
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vector<int> small_divisors = {1};
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vector<int> big_factors = {n};
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for (int i = 2; i * i <= n; i++) {
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if (n % i == 0) {
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small_divisors.push_back(i);
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big_factors.push_back(n / i);
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}
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}
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// reverse(small_divisors.begin(), small_divisors.end());
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// big_factors.insert(big_factors.end(), small_divisors.begin(), small_divisors.end());
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// return big_factors;
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reverse(big_factors.begin(), big_factors.end());
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small_divisors.insert(small_divisors.end(), big_factors.begin(), big_factors.end());
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return small_divisors;
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}
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/// 需要保证 sorted_cut_sticks 有序；需要保证 target_length 是总长度的因数
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bool verify_length_greedy(vector<int> sorted_cut_sticks, const int target_length) {
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// if (target_times == 0) { return true; }
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// if (sorted_cut_sticks.empty()) { throw logic_error("Invalid target_times"); }
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if (sorted_cut_sticks.empty()) { return true; }
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if (sorted_cut_sticks.back() > target_length) { return false; }
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int remaining_length = target_length - sorted_cut_sticks.back();
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sorted_cut_sticks.pop_back();
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if (remaining_length == 0) {
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return verify_length_greedy(sorted_cut_sticks, target_length);
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}
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while (true) {
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auto closest_iter = lower_bound(sorted_cut_sticks.begin(), sorted_cut_sticks.end(), remaining_length);
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if (closest_iter != sorted_cut_sticks.end() && *closest_iter == remaining_length) {
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sorted_cut_sticks.erase(closest_iter);
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// log_vector(sorted_cut_sticks, "after erase: ");
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return verify_length_greedy(sorted_cut_sticks, target_length);
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}
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if (closest_iter == sorted_cut_sticks.begin()) { // 都太长了！
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return false;
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}
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closest_iter -= 1; // 第一个小于 remaining_length 的元素的 iter
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remaining_length -= *closest_iter;
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sorted_cut_sticks.erase(closest_iter);
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}
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}
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int get_shortest_original_length(vector<int> cut_sticks) {
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sort(cut_sticks.begin(), cut_sticks.end());
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const int total_length = accumulate(cut_sticks.begin(), cut_sticks.end(), 0);
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const vector<int> divisors = get_divisors(total_length);
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log_vector(divisors, "divisors: ");
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for (const int divisor : divisors) {
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if (verify_length_greedy(cut_sticks, divisor)) {
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return divisor;
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}
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}
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return -1;
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}
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int main() {
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ios::sync_with_stdio(false);
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cin.tie(nullptr);
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int cut_sticks_amount;
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while (cin >> cut_sticks_amount && cut_sticks_amount) {
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vector<int> cut_sticks(cut_sticks_amount);
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for (int i = 0; i < cut_sticks_amount; i++) {
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cin >> cut_sticks[i];
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}
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sort(cut_sticks.begin(), cut_sticks.end());
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log_vector(cut_sticks, "cut_sticks: ");
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// int target_length;
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// cin >> target_length;
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// cout << (verify_length_greedy(cut_sticks, target_length) ? "Yes" : "No") << endl;
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cout << get_shortest_original_length(cut_sticks) << endl;
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}
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return 0;
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}
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