假设我给了:
>一系列整数iRange(即从1到iRange)和
>所需数量的组合
我想找到所有可能组合的数量并打印出所有这些组合.
例如:
给定:iRange = 5且n = 3
然后组合的数量是iRange! /((iRange!-n!)* n!)= 5! /(5-3)! * 3! = 10种组合,输出为:
123 - 124 - 125 - 134 - 135 - 145 - 234 - 235 - 245 - 345
另一个例子:
给定:iRange = 4且n = 2
然后组合的数量是iRange! /((iRange!-n!)* n!)= 4! /(4-2)! * 2! = 6种组合,输出为:
12 - 13 - 14 - 23 - 24 - 34
我到目前为止的尝试是:
#include <iostream>
using namespace std;
int iRange= 0;
int iN=0;
int fact(int n)
{
if ( n<1)
return 1;
else
return fact(n-1)*n;
}
void print_combinations(int n, int iMxM)
{
int iBigSetFact=fact(iMxM);
int iDiffFact=fact(iMxM-n);
int iSmallSetFact=fact(n);
int iNoTotComb = (iBigSetFact/(iDiffFact*iSmallSetFact));
cout<<"The number of possible combinations is: "<<iNoTotComb<<endl;
cout<<" and these combinations are the following: "<<endl;
int i, j, k;
for (i = 0; i < iMxM - 1; i++)
{
for (j = i + 1; j < iMxM ; j++)
{
//for (k = j + 1; k < iMxM; k++)
cout<<i+1<<j+1<<endl;
}
}
}
int main()
{
cout<<"Please give the range (max) within which the combinations are to be found: "<<endl;
cin>>iRange;
cout<<"Please give the desired number of combinations: "<<endl;
cin>>iN;
print_combinations(iN,iRange);
return 0;
}
我的问题:
与组合打印相关的代码部分仅适用于n = 2,iRange = 4,并且我无法使其一般工作,即对于任何n和iRange.
解决方法:
以下是您编写的代码:D:D,带有递归解决方案:
#include <iostream>
int iRange=0;
int iN=0; //Number of items taken from iRange, for which u want to print out the combinations
int iTotalCombs=0;
int* pTheRange;
int* pTempRange;
int find_factorial(int n)
{
if ( n<1)
return 1;
else
return find_factorial(n-1)*n;
}
//--->Here is another solution:
void print_out_combinations(int *P, int K, int n_i)
{
if (K == 0)
{
for (int j =iN;j>0;j--)
std::cout<<P[j]<<" ";
std::cout<<std::endl;
}
else
for (int i = n_i; i < iRange; i++)
{
P[K] = pTheRange[i];
print_out_combinations(P, K-1, i+1);
}
}
//Here ends the solution...
int main()
{
std::cout<<"Give the set of items -iRange- = ";
std::cin>>iRange;
std::cout<<"Give the items # -iN- of iRange for which the combinations will be created = ";
std::cin>>iN;
pTheRange = new int[iRange];
for (int i = 0;i<iRange;i++)
{
pTheRange[i]=i+1;
}
pTempRange = new int[iN];
iTotalCombs = (find_factorial(iRange)/(find_factorial(iRange-iN)*find_factorial(iN)));
std::cout<<"The number of possible combinations is: "<<iTotalCombs<<std::endl;
std::cout<<"i.e.the combinations of "<<iN<<" elements drawn from a set of size "<<iRange<<" are: "<<std::endl;
print_out_combinations(pTempRange, iN, 0);
return 0;
}