编一个程序求区间[a,b]内的所有可逆素数,满足1≤a≤b≤100000,每5个数为一行
最新回答
平凡的一天
2024-07-04 03:26:45
#include <stdio.h>
#include <stdlib.h>
//翻转给定值
unsigned
int ReverseNumber( unsigned int num )
{
int i;
unsigned int val = 0;
for( i=0; num; i++ )
{
val *= 10;
val += (num % 10);
num /= 10;
}
return val;
}
//判给定值是否为素数
int IsPrime( unsigned int num )
{
unsigned int factor;
if( num < 2 ) return 0;
for( factor=2; factor<=(num/2); factor++ )
{
if( num % factor == 0 ) return 0;
}
return 1;
}
#define MAX(a,b) ((a)>(b)?(a):(b))
#define MIN(a,b) ((a)<(b)?(a):(b))
#define MIN_VALUE 1
#define MAX_VALUE 100000
#define MAX_PER_LINE 5 //每行5个
int main( void )
{
unsigned int sv, ev, a, b, n, r, cnt = 0;
//以下代码保证用户的输入值在题目的规定条件内
do {
printf( "Please input start number: " );
scanf( "%d", &sv );
} while( (sv<MIN_VALUE) || (sv>MAX_VALUE) );
do {
printf( "Please input end number: " );
scanf( "%d", &ev );
} while( (ev<MIN_VALUE) || (ev>MAX_VALUE) );
a = MIN( sv, ev ); //较小值赋给a
b = MAX( sv, ev ); //较大值赋给b
//小于10的值直接忽略
for( n=MAX( a, 10); n<=b; )
{
r = ReverseNumber( n );
//若反序后的值与原值不等(注：反序后相等的素数叫对称素数)
if( n != r )
{
if( IsPrime( n ) && IsPrime( r ) ) //且两值均为素数
{
printf( "%d, " );
cnt++;
if( cnt % MAX_PER_LINE == 0 ) printf( "\n" ); //另起一行输出
}
}
if( n & 1 ) n += 2; //若 n 是奇数, 则每次递增步长为2
else n++; //若是偶数则加1变为奇数
}
printf( "\nCount: %d\n", cnt );
return 0;
}
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