编写函数void fun(int *x,int n),功能是：求出长度为n的数组x中的最大数与

次最大数，并把最大数和a[0]对调，次最大数和a[1]对调，其余的数保持不变。-Write a function void fun (int* x, int n), function is: find the length of the array x n the maximum number and maximum number of times, and the maximum number and a [0] reversed, the maximum number of times, and a [ 1] reversed, the number of remaining unchanged.