旋转数组
1 2 3 4 5
5 1 2 3 4
4 5 1 2 3

t = a[n - 1];
for(i = 2; i < n; i++){
    a[i] = a[i + 1];
}
a[0] = t;

翻转的函数是reverse(a, a + k)

# include <algorithm>
reverse(a, a + n);
reverse(a, a + k);
reverse(a + k, a + n);