【排队买票】 （C语言代码）

解题思路:


用递归求出总共有多少种可行的情况，再用全排列来求出总情况


注意事项:





参考代码:

#include <stdio.h>

int fact(int a)

{

int i, sum = 1;

for (i = 2;i <= a;i++)

sum *= i;

return sum;

}

int computer(int total, int one, int two, int x, int y)

{

if (y > x)

return 0;

else

{

if (x + y == total)

return 1;

else if (x == one&&y != two)

return computer(total, one, two, x, y + 1);

else if (x != one&&y == two)

return computer(total, one, two, x + 1, y);

else

return computer(total, one, two, x + 1, y) + computer(total, one, two, x, y + 1);

}

}

int main(void)

{

int one, two, total, count, sum;

while (scanf("%d%d%d", &total, &one, &two) != EOF)

{

if (one == 0)

sum = 0;

else

{

count = computer(total, one, two, 1, 0);

sum = count*fact(one)*fact(two);

}

printf("%d\n", sum);

}

return 0;

}