随机生成一个数组，长度不限，判断生成的数是否在10-40之间，如果是，则插入到数组中。再从头遍历把最大的换到数组的第一个元素-Generate a random array, the length of limitation, to determine whether the number generated between 10-40, if it is, then inserted into the array. Traversal over again for the largest ar