簡易洗牌

template <typename T>
void shuffle (T* a, int n)
{
    //暫時變數放內圈, 使得『多數舊式』編譯器可以最佳化
    while (n > 1)
    {
        int j = rand() % n;
        n--;
        T t (a[j]); a[j] = a[n]; a[n] = t;
    }
}

測試：

#include <time.h>
#include <conio.h>
#include <iostream>

using namespace std;

struct Num {int i;};

int main ()
{
    srand(time(0));

    int  a[10] = {0,1,2,3,4,5,6,7,8,9};
    char b[  ] = "abcdefghij";
    Num  c[10] = {0,1,2,3,4,5,6,7,8,9};    
    
    shuffle (a, 10);
    shuffle (b, 10);
    shuffle (c, 10);

    int i;
    puts(""); for (i=0;i<10;++i) cout <<' '<<a[i];
    puts(""); for (i=0;i<10;++i) cout <<' '<<b[i];
    puts(""); for (i=0;i<10;++i) cout <<' '<<c[i].i;

    return getch();
}