40 lines
983 B
C++
40 lines
983 B
C++
#include <chrono>
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#include <iostream>
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#include <vector>
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#include <gmpxx.h>
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using big_int = mpz_class;
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big_int partitions(int n) {
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std::vector<big_int> p(n + 1);
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p[0] = 1;
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for (int i = 1; i <= n; ++i) {
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for (int k = 1;; ++k) {
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int j = (k * (3*k - 1))/2;
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if (j > i)
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break;
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if (k & 1)
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p[i] += p[i - j];
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else
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p[i] -= p[i - j];
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j = (k * (3*k + 1))/2;
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if (j > i)
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break;
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if (k & 1)
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p[i] += p[i - j];
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else
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p[i] -= p[i - j];
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}
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}
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return p[n];
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}
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int main() {
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auto start = std::chrono::steady_clock::now();
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auto result = partitions(6666);
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auto end = std::chrono::steady_clock::now();
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std::chrono::duration<double, std::milli> ms(end - start);
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std::cout << result << '\n';
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std::cout << "elapsed time: " << ms.count() << " milliseconds\n";
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}
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