美素数备忘

#include<stdio.h>
#include<math.h>
#define maxn 1000000+1

int prime[maxn];
int count[maxn];
bool is_beauty_prime(int n);
int tot = 0;
void getPrime()
{
int i, j;
int tmp = int((double)sqrt(maxn) + 1);
for(i = 2; i < maxn; i++)
{
prime[i] = 1;
}
for(i = 2; i < maxn; i++)
{
if(prime[i])
{
if(i < tmp)
{
for(j = i*i; j < maxn; j+=i)
prime[j] = 0;
}
}
}
for(i = 2; i < maxn; i++)
{
if(prime[i] && is_beauty_prime(i))
{
count[++tot] = i;
}
}
}

bool is_beauty_prime(int n)
{
int tmp = 0;
while(n)
{
tmp += n%10;
n /= 10;
}
if(prime[tmp])
return true;
return false;
}
int binary_search(int l, int h, int num)
{
while(l <= h)
{
int mid = (l+h)/2;
if(num == count[mid])
return mid;
else if(count[mid] > num)
{
h = mid-1;
}
else
{
l = mid+1;
}
}
return l;
}

int beauty_prime(int a, int b)
{
int i;
int sum = 0;
for(i = a; i <= b; i++)
{
if(prime[i])
{
if(is_beauty_prime(i))
sum++;
}
}
return sum;
}

int main()
{
int n, a, b, i, j;
getPrime();

scanf("%d", &n);
for(i = 1; i <= n; i++)
{
int top = 0;
int down = 0;
scanf("%d %d", &a, &b);
down = binary_search(1, tot, a);
top = binary_search(1, tot, b);
if(count[top] == b)top++;
down--;
int num = top-down-1;
printf("Case #%d: %d\n", i, num);
}
}