用磁盘调度算法编写代码要求分别FCFS、SSTF、SCAN、C-SCAN

以下是四种磁盘调度算法的代码实现：

1. FCFS（先来先服务）

def fcfs(current, requests):
    total_distance = 0
    for request in requests:
        total_distance += abs(request - current)
        current = request
    return total_distance

2. SSTF（最短寻道时间优先）

def sstf(current, requests):
    total_distance = 0
    while requests:
        shortest_distance = float('inf')
        shortest_index = None
        for i, request in enumerate(requests):
            distance = abs(request - current)
            if distance < shortest_distance:
                shortest_distance = distance
                shortest_index = i
        request = requests.pop(shortest_index)
        total_distance += shortest_distance
        current = request
    return total_distance

3. SCAN（扫描算法）

def scan(current, requests, direction='right'):
    total_distance = 0
    if direction == 'right':
        sorted_requests = sorted(requests)
    else:
        sorted_requests = sorted(requests, reverse=True)
    index = 0
    while index < len(sorted_requests) and sorted_requests[index] < current:
        index += 1
    while index < len(sorted_requests):
        request = sorted_requests[index]
        total_distance += abs(request - current)
        current = request
        index += 1
    if direction == 'right':
        total_distance += abs(current - max(requests))
        current = max(requests)
    else:
        total_distance += abs(current - min(requests))
        current = min(requests)
    index -= 1
    while index >= 0:
        request = sorted_requests[index]
        total_distance += abs(request - current)
        current = request
        index -= 1
    return total_distance

4. C-SCAN（循环扫描算法）

def c_scan(current, requests, direction='right'):
    total_distance = 0
    if direction == 'right':
        sorted_requests = sorted(requests)
    else:
        sorted_requests = sorted(requests, reverse=True)
    index = 0
    while index < len(sorted_requests) and sorted_requests[index] < current:
        index += 1
    while index < len(sorted_requests):
        request = sorted_requests[index]
        total_distance += abs(request - current)
        current = request
        index += 1
    if direction == 'right':
        total_distance += abs(current - max(requests))
        current = max(requests)
        index = 0
    else:
        total_distance += abs(current - min(requests))
        current = min(requests)
        index = len(sorted_requests) - 1
    while index >= 0:
        request = sorted_requests[index]
        total_distance += abs(request - current)
        current = request
        index -= 1
    if direction == 'right':
        total_distance += abs(current - min(requests))
    else:
        total_distance += abs(current - max(requests))
    return total_distance

以上四种算法的实现均接收当前磁头位置和请求序列作为输入，返回总的寻道距离。其中 SCAN 和 C-SCAN 还接收运动方向参数，可以选择从内向外或从外向内扫描。