emmm
线性筛+前缀和水题
代码
#include<iostream> #include<cstdio> #include<algorithm> #include<cmath> using namespace std; int n,m,emm[1000500]; int sum[1000500]; inline void xxss(int a) { sum[2]=1; for (int i=2;i<=a;++i) { if (!emm[i]) { for (int j=1;j*i<=a;++j) emm[j*i]=1; sum[i]=sum[i-1]+1; } else sum[i]=sum[i-1]; } return ; } inline int read() { int wc=0,emm=1; char c=getchar(); while(c<'0'||c>'9') { c=getchar();if (c=='-') emm=-1; } while(c>='0'&&c<='9') wc=wc*10+c-'0',c=getchar(); return wc*emm; } int main() { int x,y; scanf("%d%d",&n,&m); xxss(m); while (n--) { int ans=0; x=read();y=read(); if (x<1||y>m) printf("Crossing the line\n"); else { printf("%d\n",sum[y]-sum[x-1]); } } return 0; }