[UVa]10789:Prime Frequency

利用質數表和ASCII碼就可以快速解完此題。

[C](0.016)

	#include<stdio.h>
	#include<string.h>
	int main()
	{
	int prime[2005] = {1, 1, 0, 0};
	int i, j;
	for( i = 2 ; i < 2001 ; i++ )
	if( !prime[i] )
	for( j = i*i ; j < 2001 ; j += i )
	prime[j] = 1;
	int T;
	while( scanf( "%d", &T ) != EOF )
	{
	getchar();
	char str[2005];
	for( i = 1 ; i <= T ; i++ )
	{
	gets( str );
	int strlength = strlen( str );
	int ASCII[256] = {0};
	for( j = 0 ; j < strlength ; j++ )
	ASCII[str[j]]++;
	printf( "Case %d: ", i );
	int ok = 0;
	for( j = 0 ; j < 128 ; j++ )
	if( !prime[ASCII[j]] )
	{
	ok = 1;
	printf( "%c", j );
	}
	if( !ok )
	printf( "empty" );
	printf( "\n" );
	}
	}
	return 0;
	}

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