令S为一个n个正整数的集合，n为偶数。请设计一个有效的算法将S分成两个子集S1，S2，且两个子集均含n/2个元素。结果输出到文件中-Let S be a set of positive integers n, n is an even number. Please design an efficient algorithm S into two subsets S1, S2, and the two subsets are inclusive of n/2 elements. Output to