24 lines
635 B
C++
24 lines
635 B
C++
//欧拉筛
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const int N = 1e5 + 10;
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int primes[N], cnt; // primes[]存储所有素数
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bool st[N]; // st[x]存储x是否被筛掉
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void get_primes(int n) {
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for (int i = 2; i <= n; i++) {
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if (!st[i]) primes[cnt++] = i;
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for (int j = 0; primes[j]*i <= n; j++) {
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st[primes[j] * i] = true;
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if (i % primes[j] == 0) break;
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}
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}
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}
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void get_primes(int n){
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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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for (int j = 0; primes[j] * i <= n;j++){
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st[primes[j] * i] = true;
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if(i%primes[j]==0)
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break;
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}
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}
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} |