说明：  通过初始化或者用户输入两个数组a和b，求两个数组的和差并输出，所谓和差就是去掉两个数组中相同的元素 然后将两个数组中的元素存放在一个新的数组中，且数组A中元素要在B数组元素之前
(Through the initialization or user input two arrays a and B, for the two array and difference and output, and the difference is called to remove the same two elements in the array and the two elements in the array is stored in a new array, and the elements in the array A before B array elements)