zoj 1312 || poj 1595 Prime Cuts

给你数n c，求在1-n中的素数，如果这个素数序列为奇数，求中间c*2-1个素数，偶数则求c*2个素数。

 

很基本的，先打表，然后我的做法是，把最开始那个表素数里存成纯素数表中的编号，然后下面就简单了，细节处理注意一下就好了。

 

#include <queue>#include <stack>#include <math.h>#include <stdio.h>#include <stdlib.h>#include <iostream>#include <limits.h>#include <string.h>#include <algorithm>#define MAX 30000using namespace std;int pri[MAX];int a[MAX];void init(){int i,j;memset(a,0,sizeof(a));for(i=1; i<MAX; i++)a[i] = 1;a[1] = 1;for(i=2; i<MAX; i++)for(j=2; j*i<MAX; j++)if( a[i] == 1 )a[i*j] = 0;int num = 1;for(i=1; i<MAX; i++)if( a[i] == 1 ){a[i] = num;pri[num] = i;num++;}}int main(){int n,i,k,c;init();while( ~scanf("%d%d",&n,&c) ){int ind = n;printf("%d %d:",n,c);while( a[ind] == 0 )ind--;int num = a[ind];if( num % 2 == 0 && c*2 >= num || num % 2 == 1 && c*2-1 >= num ){for(i=1; i<=num; i++)printf(" %d",pri[i]);printf("/n/n");continue;}if( num % 2 == 0 ){k = c*2;num = num/2-c+1;}else{k = c*2-1;num = num/2-c/2+1;}for(i=num; i<num+k; i++)printf(" %d",pri[i]);printf("/n/n");}return 0;}