5：将一个5*5的矩阵中最大的元素放在中心，

四个角分别放四个最小的元素(顺序从左到右，从

上到下顺序依次从小到大存放)，写一个函数实现

之。-5: a 5* 5 matrix elements on the center, four corners, respectively, put the four smallest elements (in order from left to right, top to bottom in the order from small to large storage), write a function of.