银行家算法的C语言、Java和Python实现

银行家算法是一种用于避免死锁的资源分配算法。它通过动态地检查系统中的资源分配请求，以确保分配后不会导致死锁的发生。

下面是分别使用C语言、Java和Python实现的银行家算法示例，并附带详细的注释。

1.C语言实现

#include <stdio.h>

// 定义最大进程数和资源数
#define MAX_PROCESS 5
#define MAX_RESOURCE 3

// 定义可用资源、最大需求和已分配资源的数组
int available[MAX_RESOURCE];
int max[MAX_PROCESS][MAX_RESOURCE];
int allocation[MAX_PROCESS][MAX_RESOURCE];

// 定义需要计算的进程数和资源数
int num_process, num_resource;

// 检查是否存在安全序列的函数
int isSafe() {
    int work[MAX_RESOURCE];
    int finish[MAX_PROCESS] = {0};
    int need[MAX_PROCESS][MAX_RESOURCE];

    // 初始化工作向量和需求矩阵
    for (int i = 0; i < num_resource; i++) {
        work[i] = available[i];
        for (int j = 0; j < num_process; j++) {
            need[j][i] = max[j][i] - allocation[j][i];
        }
    }

    int count = 0;
    while (count < num_process) {
        int found = 0;
        for (int i = 0; i < num_process; i++) {
            if (!finish[i]) {
                int j;
                for (j = 0; j < num_resource; j++) {
                    if (need[i][j] > work[j])
                        break;
                }
                if (j == num_resource) {
                    for (int k = 0; k < num_resource; k++) {
                        work[k] += allocation[i][k];
                    }
                    finish[i] = 1;
                    found = 1;
                    count++;
                }
            }
        }
        if (!found)
            break;
    }

    return (count == num_process);
}

int main() {
    // 输入进程数和资源数
    printf("请输入进程数：");
    scanf("%d", &num_process);
    printf("请输入资源数：");
    scanf("%d", &num_resource);

    // 输入可用资源向量
    printf("请输入可用资源向量：\n");
    for (int i = 0; i < num_resource; i++) {
        scanf("%d", &available[i]);
    }

    // 输入最大需求矩阵
    printf("请输入最大需求矩阵：\n");
    for (int i = 0; i < num_process; i++) {
        printf("请输入进程 %d 的最大需求：\n", i);
        for (int j = 0; j < num_resource; j++) {
            scanf("%d", &max[i][j]);
        }
    }

    // 输入已分配资源矩阵
    printf("请输入已分配资源矩阵：\n");
    for (int i = 0; i < num_process; i++) {
        printf("请输入进程 %d 的已分配资源：\n", i);
        for (int j = 0; j < num_resource; j++) {
            scanf("%d", &allocation[i][j]);
        }
    }

    // 检查是否存在安全序列
    if (isSafe()) {
        printf("存在安全序列！\n");
    } else {
        printf("不存在安全序列！\n");
    }

    return 0;
}

2.Java实现

import java.util.Scanner;

public class BankersAlgorithm {

    // 定义最大进程数和资源数
    private static final int MAX_PROCESS = 5;
    private static final int MAX_RESOURCE = 3;

    // 定义可用资源、最大需求和已分配资源的数组
    private static int[] available = new int[MAX_RESOURCE];
    private static int[][] max = new int[MAX_PROCESS][MAX_RESOURCE];
    private static int[][] allocation = new int[MAX_PROCESS][MAX_RESOURCE];

    // 定义需要计算的进程数和资源数
    private static int numProcess, numResource;

    // 检查是否存在安全序列的方法
    private static boolean isSafe() {
        int[] work = new int[MAX_RESOURCE];
        int[] finish = new int[MAX_PROCESS];
        int[][] need = new int[MAX_PROCESS][MAX_RESOURCE];

        // 初始化工作向量和需求矩阵
        for (int i = 0; i < numResource; i++) {
            work[i] = available[i];
            for (int j = 0; j < numProcess; j++) {
                need[j][i] = max[j][i] - allocation[j][i];
            }
        }

        int count = 0;
        while (count < numProcess) {
            boolean found = false;
            for (int i = 0; i < numProcess; i++) {
                if (finish[i] == 0) {
                    int j;
                    for (j = 0; j < numResource; j++) {
                        if (need[i][j] > work[j]) {
                            break;
                        }
                    }
                    if (j == numResource) {
                        for (int k = 0; k < numResource; k++) {
                            work[k] += allocation[i][k];
                        }
                        finish[i] = 1;
                        found = true;
                        count++;
                    }
                }
            }
            if (!found) {
                break;
            }
        }

        return (count == numProcess);
    }

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);

        // 输入进程数和资源数
        System.out.print("请输入进程数：");
        numProcess = scanner.nextInt();
        System.out.print("请输入资源数：");
        numResource = scanner.nextInt();

        // 输入可用资源向量
        System.out.println("请输入可用资源向量：");
        for (int i = 0; i < numResource; i++) {
            available[i] = scanner.nextInt();
        }

        // 输入最大需求矩阵
        System.out.println("请输入最大需求矩阵：");
        for (int i = 0; i < numProcess; i++) {
            System.out.println("请输入进程 " + i + " 的最大需求：");
            for (int j = 0; j < numResource; j++) {
                max[i][j] = scanner.nextInt();
            }
        }

        // 输入已分配资源矩阵
        System.out.println("请输入已分配资源矩阵：");
        for (int i = 0; i < numProcess; i++) {
            System.out.println("请输入进程 " + i + " 的已分配资源：");
            for (int j = 0; j < numResource; j++) {
                allocation[i][j] = scanner.nextInt();
            }
        }

        // 检查是否存在安全序列
        if (isSafe()) {
            System.out.println("存在安全序列！");
        } else {
            System.out.println("不存在安全序列！");
        }

        scanner.close();
    }
}

3.Python实现

def is_safe():
    work = available[:]
    finish = [0] * num_process
    need = [[max[i][j] - allocation[i][j] for j in range(num_resource)] for i in range(num_process)]

    count = 0
    while count < num_process:
        found = False
        for i in range(num_process):
            if finish[i] == 0:
                for j in range(num_resource):
                    if need[i][j] > work[j]:
                        break
                else:
                    for k in range(num_resource):
                        work[k] += allocation[i][k]
                    finish[i] = 1
                    found = True
                    count += 1
        if not found:
            break

    return count == num_process


# 输入进程数和资源数
num_process = int(input("请输入进程数："))
num_resource = int(input("请输入资源数："))

# 输入可用资源向量
print("请输入可用资源向量：")
available = list(map(int, input().split()))

# 输入最大需求矩阵
print("请输入最大需求矩阵：")
max = []
for i in range(num_process):
    print("请输入进程", i, "的最大需求：")
    row = list(map(int, input().split()))
    max.append(row)

# 输入已分配资源矩阵
print("请输入已分配资源矩阵：")
allocation = []
for i in range(num_process):
    print("请输入进程", i, "的已分配资源：")
    row = list(map(int, input().split()))
    allocation.append(row)

# 检查是否存在安全序列
if is_safe():
    print("存在安全序列！")
else:
    print("不存在安全序列！")

通过理解和使用银行家算法，可以帮助我们更好地管理和优化资源分配，避免死锁的发生。