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 na na page number and page rate.