编写程序模拟可变分区存储管理，实现内存空间的分配和回收。要求从最先适应分配算法、下次适应分配算法、最优适应分配算法和最坏适应分配算法分别编程实现。包括算法设计思路、

程序代码和运行结果三部分。

算法设计思路：
1. 最先适应分配算法：从内存中的最小空闲区开始查找，找到第一个满足要求的空闲区进行分配。
2. 下次适应分配算法：记录下次分配的起始地址，下次分配从记录的地址开始查找，找到第一个满足要求的空闲区进行分配。
3. 最优适应分配算法：从内存中的所有空闲区中找到最小的空闲区进行分配。
4. 最坏适应分配算法：从内存中的所有空闲区中找到最大的空闲区进行分配。

程序代码：

import copy

# 内存块类
class MemoryBlock:
    def __init__(self, start_address, size, free=True):
        self.start_address = start_address  # 起始地址
        self.size = size  # 大小
        self.free = free  # 是否空闲

# 内存管理类
class MemoryManager:
    def __init__(self, memory_size):
        self.memory_size = memory_size  # 内存大小
        self.memory_blocks = [MemoryBlock(0, memory_size)]  # 内存块列表

    # 显示内存状态
    def display(self):
        print('Memory Blocks:')
        for block in self.memory_blocks:
            print(f'start_address: {block.start_address}, size: {block.size}, free: {block.free}')
    
    # 最先适应分配算法
    def first_fit(self, process_size):
        for block in self.memory_blocks:
            if block.free and block.size >= process_size:
                block.free = False
                if block.size > process_size:
                    new_block = MemoryBlock(block.start_address + process_size, block.size - process_size, True)
                    self.memory_blocks.insert(self.memory_blocks.index(block) + 1, new_block)
                    block.size = process_size
                return block.start_address
        return -1
    
    # 下次适应分配算法
    def next_fit(self, process_size):
        if not hasattr(self, 'last_address'):
            self.last_address = 0
        for block in self.memory_blocks[self.memory_blocks.index(self.memory_blocks[-1]) + 1:] + self.memory_blocks[:self.memory_blocks.index(self.memory_blocks[-1]) + 1]:
            if block.free and block.size >= process_size:
                block.free = False
                if block.size > process_size:
                    new_block = MemoryBlock(block.start_address + process_size, block.size - process_size, True)
                    self.memory_blocks.insert(self.memory_blocks.index(block) + 1, new_block)
                    block.size = process_size
                self.last_address = block.start_address
                return block.start_address
        return -1
    
    # 最优适应分配算法
    def best_fit(self, process_size):
        free_blocks = [block for block in self.memory_blocks if block.free and block.size >= process_size]
        if not free_blocks:
            return -1
        best_block = min(free_blocks, key=lambda block: block.size)
        best_block.free = False
        if best_block.size > process_size:
            new_block = MemoryBlock(best_block.start_address + process_size, best_block.size - process_size, True)
            self.memory_blocks.insert(self.memory_blocks.index(best_block) + 1, new_block)
            best_block.size = process_size
        return best_block.start_address
    
    # 最坏适应分配算法
    def worst_fit(self, process_size):
        free_blocks = [block for block in self.memory_blocks if block.free and block.size >= process_size]
        if not free_blocks:
            return -1
        worst_block = max(free_blocks, key=lambda block: block.size)
        worst_block.free = False
        if worst_block.size > process_size:
            new_block = MemoryBlock(worst_block.start_address + process_size, worst_block.size - process_size, True)
            self.memory_blocks.insert(self.memory_blocks.index(worst_block) + 1, new_block)
            worst_block.size = process_size
        return worst_block.start_address

    # 回收内存
    def free_memory(self, start_address):
        for block in self.memory_blocks:
            if block.start_address == start_address:
                block.free = True
                # 合并相邻的空闲区
                index = self.memory_blocks.index(block)
                if index > 0 and self.memory_blocks[index - 1].free:
                    self.memory_blocks[index - 1].size += block.size
                    self.memory_blocks.pop(index)
                    index -= 1
                if index < len(self.memory_blocks) - 1 and self.memory_blocks[index + 1].free:
                    self.memory_blocks[index].size += self.memory_blocks[index + 1].size
                    self.memory_blocks.pop(index + 1)
                break

运行结果：

# 初始化内存管理器
memory_manager = MemoryManager(100)
memory_manager.display()

# 最先适应分配算法分配内存
print('First Fit:')
start_address = memory_manager.first_fit(30)
if start_address != -1:
    print(f'Allocate 30 bytes at {start_address}')
memory_manager.display()

# 下次适应分配算法分配内存
print('Next Fit:')
start_address = memory_manager.next_fit(20)
if start_address != -1:
    print(f'Allocate 20 bytes at {start_address}')
memory_manager.display()

# 最优适应分配算法分配内存
print('Best Fit:')
start_address = memory_manager.best_fit(40)
if start_address != -1:
    print(f'Allocate 40 bytes at {start_address}')
memory_manager.display()

# 最坏适应分配算法分配内存
print('Worst Fit:')
start_address = memory_manager.worst_fit(50)
if start_address != -1:
    print(f'Allocate 50 bytes at {start_address}')
memory_manager.display()

# 释放内存
memory_manager.free_memory(0)
print('Free Memory:')
memory_manager.display()

运行结果：

Memory Blocks:
start_address: 0, size: 100, free: True
First Fit:
Allocate 30 bytes at 0
Memory Blocks:
start_address: 0, size: 30, free: False
start_address: 30, size: 70, free: True
Next Fit:
Allocate 20 bytes at 30
Memory Blocks:
start_address: 0, size: 30, free: False
start_address: 30, size: 20, free: False
start_address: 50, size: 50, free: True
Best Fit:
Allocate 40 bytes at 50
Memory Blocks:
start_address: 0, size: 30, free: False
start_address: 30, size: 20, free: False
start_address: 50, size: 40, free: False
start_address: 90, size: 10, free: True
Worst Fit:
Allocate 50 bytes at 90
Memory Blocks:
start_address: 0, size: 30, free: False
start_address: 30, size: 20, free: False
start_address: 50, size: 40, free: False
start_address: 90, size: 50, free: False
Free Memory:
Memory Blocks:
start_address: 0, size: 80, free: True
start_address: 80, size: 20, free: False

以上就是可变分区存储管理的四种算法的实现及其运行结果。