Question

C语言程序设计：随便输入四个数，只能用四则运算，看这四个数能否算出二十四点。

要求程序能给出所有的算法（加乘减除），使得4个数经过运算可以得到二十四点

Answer 1

#include <stdio.h>
#include <string.h>
int c24;
char expr3[80];
char expr4[80];
void count2( int a, int b )
{
if ( a + b == 24 )
{
c24 ++;
printf( "%s\t%s\t%d+%d=24\n", expr4, expr3, a, b );
}
if ( a * b == 24 )
{
c24 ++;
printf( "%s\t%s\t%d+%d=24\n", expr4, expr3, a, b );
}
if ( a * b == 24 )
{
c24 ++;
printf( "%s\t%s\t%d*%d=24\n", expr4, expr3, a, b );
}
if ( a - b == 24 )
{
c24 ++;
printf( "%s\t%s\t%d-%d=24\n", expr4, expr3, a, b );
}
if ( b - a == 24 )
{
c24 ++;
printf( "%s\t%s\t%d-%d=24\n", expr4, expr3, b, a );
}
if ( (b!=0) && (a==24*b) )
{
c24 ++;
printf( "%s\t%s\t%d/%d=24\n", expr4, expr3, a, b );
}
if ( (a!=0) && (b==24*a) )
{
c24 ++;
printf( "%s\t%s\t%d/%d=24\n", expr4, expr3, b, a );
}
}
void count3( int a, int b, int c )
{
int dd[3];
int i,j,k,nd;
dd[0] = a;
dd[1] = b;
dd[2] = c;
for ( i = 0; i < 3; i++ )
for ( j = i+1; j < 3; j++ )
{
k = 3 - i - j;
nd = dd[i] + dd[j];
sprintf( expr3, "%d+%d=%d", dd[i], dd[j], nd );
count2( nd, dd[k] );
nd = dd[i] * dd[j];
sprintf( expr3, "%d*%d=%d", dd[i], dd[j], nd );
count2( nd, dd[k] );
if ( dd[i]>dd[j] )
{
nd = dd[i] - dd[j];
sprintf( expr3, "%d-%d=%d", dd[i], dd[j], nd );
}
else
{
nd = dd[j] - dd[i];
sprintf( expr3, "%d-%d=%d", dd[j], dd[i], nd );
}
count2( nd, dd[k] );
if ( (dd[j]!=0) && (dd[i]%dd[j]==0) )
{
nd = dd[i] / dd[j];
sprintf( expr3, "%d/%d=%d", dd[i], dd[j], nd );
count2( nd, dd[k] );
}
else if ( (dd[i]!=0) && (dd[j]%dd[i]==0) )
{
nd = dd[j] / dd[i];
sprintf( expr3, "%d/%d=%d", dd[j], dd[i], nd );
count2( nd, dd[k] );
}
}
}
void count4( int a, int b, int c, int d )
{
int dd[4];
int i,j,k,m,nd; dd[0] = a;
dd[1] = b;
dd[2] = c;
dd[3] = d;
for ( i = 0; i < 4; i++ )
for ( j = i+1; j < 4; j++ )
{
for ( k = 0; (k==i) || (k==j); k++ ) ;
m = 6 - i - j - k;
nd = dd[i] + dd[j];
sprintf( expr4, "%d+%d=%d", dd[i], dd[j], nd );
count3( nd, dd[k], dd[m] );
nd = dd[i] * dd[j];
sprintf( expr4, "%d*%d=%d", dd[i], dd[j], nd );
count3( nd, dd[k], dd[m] );
if ( dd[i]>dd[j] )
{
nd = dd[i] - dd[j];
sprintf( expr4, "%d-%d=%d", dd[i], dd[j], nd );
}
else
{
nd = dd[j] - dd[i];
sprintf( expr4, "%d-%d=%d", dd[j], dd[i], nd );
}
count3( nd, dd[k], dd[m] );
if ( (dd[j]!=0) && (dd[i]%dd[j]==0) )
{
nd = dd[j] / dd[i];
sprintf( expr4, "%d/%d=%d", dd[j], dd[i], nd );
count3( nd, dd[k], dd[m] );
}
}
}
main()
{
int a,b,c,d;
printf( "Input 4 Number for Count 24: " );
scanf( "%d%d%d%d", &a, &b, &c, &d );
c24 = 0;
count4( a, b, c, d );
if ( c24==0 )
printf( "=======failed======\n" ); /***/
printf("End of C Program, Press Enter.\n");
getchar();
getchar();
return 0;
}

Answer 2

百度知道上之前已有相关提问和回答，请参考
http://zhidao.baidu.com/question/130189305.html
(我也在学习，以上未验证，呵呵)

Answer 3

这个真忘了