银行家算法python

银行家算法是一种操作系统中用来避免死锁的算法，下面是一个简单的银行家算法的 Python 实现示例：

# 定义函数实现银行家算法
def banker_algorithm(available, maximum, allocation):
    n = len(available)
    # 初始化 need 和 work 矩阵
    need = []
    for i in range(n):
        need.append([maximum[i][j] - allocation[i][j] for j in range(len(allocation[i]))])
    work = available[:]
    finish = [False] * n
    # 模拟银行家算法
    safe_seq = []
    while False in finish:
        found = False
        for i in range(n):
            if not finish[i] and all([need[i][j] <= work[j] for j in range(len(work))]):
                finish[i] = True
                found = True
                safe_seq.append(i)
                work = [work[j] + allocation[i][j] for j in range(len(work))]
                break
        if not found:
            return None
    return safe_seq

# 测试银行家算法
if __name__ == '__main__':
    available = [3, 3, 2]
    maximum = [[7, 5, 3], [3, 2, 2], [9, 0, 2], [2, 2, 2]]
    allocation = [[0, 1, 0], [2, 0, 0], [3, 0, 2], [2, 1, 1]]
    safe_seq = banker_algorithm(available, maximum, allocation)
    if safe_seq is None:
        print('No safe sequence found!')
    else:
        print('Safe sequence: ', ' -> '.join(['P' + str(i) for i in safe_seq]))

这里的 available、maximum 和 allocation 分别表示系统可用资源、每个进程需要的最大资源和已经分配给每个进程的资源。函数的返回值是银行家算法模拟得到的安全序列，如果找不到安全序列，则返回 None。在上面的示例中，银行家算法得到的安全序列是 P1 -> P3 -> P4 -> P0。