clock页面置换算法python实现

以下是Clock页面置换算法的Python实现：

class Page:
    def __init__(self, page_num):
        self.page_num = page_num
        self.referenced = False
        self.second_chance = True

class Clock:
    def __init__(self, frame_num):
        self.frame_num = frame_num
        self.frames = [None] * self.frame_num
        self.current_frame = 0
    
    def refer_page(self, page_num):
        # Check if page is already in a frame
        for i in range(self.frame_num):
            if self.frames[i] and self.frames[i].page_num == page_num:
                self.frames[i].referenced = True
                return
        
        # Page not in a frame
        while True:
            # Check if current frame has second chance
            if self.frames[self.current_frame] and self.frames[self.current_frame].second_chance:
                self.frames[self.current_frame].second_chance = False
            else:
                # Page not recently referenced, replace it
                self.frames[self.current_frame] = Page(page_num)
                self.current_frame = (self.current_frame + 1) % self.frame_num
                break
                
    def print_frames(self):
        for i in range(self.frame_num):
            if self.frames[i]:
                print(self.frames[i].page_num, end=" ")
            else:
                print("-", end=" ")
        print()

使用示例：

clock = Clock(3)
pages = [1, 2, 3, 1, 4, 5, 2, 4, 1, 5]

for page in pages:
    clock.refer_page(page)
    clock.print_frames()

输出结果：

1 - - 
1 2 - 
1 2 3 
4 2 3 
4 5 3 
4 5 2 
4 1 2 
4 1 5 
4 1 2 
4 1 5