说明：  有两个数组a,b，大小都为n,数组元素的值任意，无序； 要求：通过交换a,b中的元素，使数组a元素的和与数组b元素的和之间的差最小
(There are two arrays a, b, large and small for n, the value of the element array of arbitrary and disorderly requirements: through the exchange of a, b of elements to the array a elements and elements of the array b and the difference between the minimum)