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37 lines
1.1 KiB
37 lines
1.1 KiB
#include <bits/stdc++.h>
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using namespace std;
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const int N = 1010;
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int primes[N]; //保存的是每一个质数
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int cnt; //cnt代表质数下标,就是到第几个了
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int phi[N]; //欧拉函数值
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bool st[N]; //是不是已经被筛掉了
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// 求1-N之间每一个数的欧拉函数
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// 线性筛法求质数的过程当中，捎带着求出每个数的欧拉函数值,其实还可以顺便求出很多东西。
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void get_eulers(int n) {
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phi[1] = 1;
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for (int i = 2; i <= n; i++) {
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if (!st[i]) {
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primes[cnt++] = i;
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phi[i] = i - 1;
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}
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for (int j = 0; primes[j] <= n / i; j++) {
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int t = primes[j] * i;
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st[t] = true;
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if (i % primes[j] == 0) {
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phi[t] = phi[i] * primes[j];
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break;
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} else {
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phi[t] = phi[i] * (primes[j] - 1);
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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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get_eulers(1000);
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for (int i = 1; i <= 1000; i++)
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cout << i << ":" << phi[i] << endl;
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return 0;
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} |