分别实现最佳置换算法(optimal)、先进先出(FIFO)页面置换算法和最近最久未使用（LRU）置换算法，并给出各算法缺页次数和缺页率。-respectively optimal replacement algorithm (optimal), FIFO (FIFO) page replacement algorithm and the most recent time on the use (LRU) replacement algorithm, the algorithm is given