[UVa]10394:Twin Primes

建質數表得解。

[C](1.492)

	#include<stdio.h>
	int prime[20000001] = { 1, 1, 0 };
	int answer[100005] = {0};
	int allanswer = 1;
	int main()
	{
	long long i, j;
	for( i = 3 ; i < 20000000L && allanswer <= 100000 ; i+=2 )
	if( !prime[i] )
	{
	for( j = i*i ; j < 20000000L ; j += i )
	prime[j] = 1;
	if( !prime[i] && !prime[i-2] )
	answer[allanswer++] = i-2;
	}
	int S;
	while( scanf( "%d", &S ) != EOF )
	printf( "(%d, %d)\n", answer[S], answer[S]+2 );
	return 0;
	}

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