zuhe.cpp

给出从m个数中取n个数的所有组合,解决了组合数学中的一个难题,例如从6中取4个具体情况怎样,本程序给出(1,2,3,4)(1,2,3,5)....等等每一种取法.

#include <stdio.h>
#include <stdlib.h>
//计算组合数
int Zuhe(int m, int n)
{
int sum2=1;
int sum1=1;
int sum=1;
int j;
int i;
for( i=m, j=n; i>=m-n+1; i--)
{sum1=sum1*i;}
for( i=1; i<=n; i++)
{sum2=sum2*i;}
sum=sum1/sum2;
return(sum);

}
//从后向前扫描数组p,q返回第一个扫描到的P[i]<q[i]的坐标i
int findmaxindex(int* p, int* q, int m)
{
int i;
for(i=m-1; i>=0; i--)
{if(p[i]<q[i])
    return(i);
  
}
}
//在数组p的第i 个元素加一并存回，再依次加一存入下一个，从而改变原数组的值
void Next(int* p, int i, int m)
{
int j;
p[i]=p[i]+1;
for(j=i; j<=m-1;j++)
{
   p[j+1]=p[j]+1;
}
for( j=0; j<=m-1;j++)
{
   printf("%4d",p[j]);
  
}
printf("\n");
}




void main()
{
int Numberspace=0;
int Choose=0;
int* PchooseB=0;
int* PchooseE=0;
int k=0;
int i;
printf("Input total number:");
scanf("%d",&Numberspace);
if(Numberspace<=0||Numberspace>15)
{
   printf("Maybe too large or too small\n");
  
   return;
}
printf("\nHow many number you want to choose:");
scanf("%d", &Choose);
if(Choose>Numberspace)
{
   printf("Input Error");
  
   return;
}
PchooseB=(int*)malloc(sizeof(int)*Choose);
PchooseE=(int*)malloc(sizeof(int)*Choose);
for( i=0; i<Choose; i++)
{
   PchooseB[i]=i+1;
   printf("%4d",PchooseB[i]);

}
printf("\n");

for( i=0; i<Choose; i++)
{
   PchooseE[i]=Numberspace-Choose+i+1;
}

for( i=1; i<=Zuhe(Numberspace,Choose)-1; i++)
{
   k=findmaxindex(PchooseB, PchooseE, Choose);
   Next(PchooseB, k, Choose);
}
printf("共有%d个组合\n",Zuhe(Numberspace,Choose));
scanf("%d",&k);

}