Qualifiied Primes--埃式筛素数

题目：给出一个闭区间，和一个数，问该区间中包含几个含有该数的素数

分析：直接上埃法就行。

Code：

#include <cstdio>#include <cstring>#include <cmath>#include <algorithm>using namespace std;const int maxn = 4000000+5;bool nprime[maxn];int ans;char c[maxn];void init() {memset(nprime, 0, sizeof(nprime));nprime[0] = nprime[1] = 1;for(int i = 2; i < maxn; i++) {if(!nprime[i]) {for(int j = i+i; j < maxn; j += i)nprime[j] = 1;}}}int main() {init();int a, b, d;while(scanf("%d%d%d", &a, &b, &d) != EOF) {ans = 0;for(int i = a; i <= b; i++) {if(!nprime[i]) {sprintf(c, "%d", i);int len = strlen(c);for(int j = 0; j < len; j++)if(c[j] == '0'+d) {ans++;break;}}}printf("%d\n", ans);}return 0;}