操作系统银行家算法用c语言写出来

银行家算法是一种用于避免死锁的算法，用于在多进程系统中管理资源分配。该算法通过模拟分配资源来测试是否会导致死锁，确保系统始终处于安全状态。

下面是一个用C语言实现银行家算法的示例。此程序包括初始化系统状态、处理资源请求并检查系统是否处于安全状态的功能。

步骤一：定义结构和全局变量

c
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#include <stdio.h>
#include <stdbool.h>

#define NUM_PROCESSES 5
#define NUM_RESOURCES 3

int available[NUM_RESOURCES]; // 可用资源数
int maximum[NUM_PROCESSES][NUM_RESOURCES]; // 最大需求矩阵
int allocation[NUM_PROCESSES][NUM_RESOURCES]; // 分配矩阵
int need[NUM_PROCESSES][NUM_RESOURCES]; // 需求矩阵

void initializeSystem();
bool isSafeState();
bool requestResources(int process_id, int request[]);
void releaseResources(int process_id, int release[]);

步骤二：初始化系统状态

c
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void initializeSystem() {
    // 初始化可用资源数
    available[0] = 3;
    available[1] = 3;
    available[2] = 2;

    // 初始化最大需求矩阵
    int max[NUM_PROCESSES][NUM_RESOURCES] = {
        {7, 5, 3},
        {3, 2, 2},
        {9, 0, 2},
        {2, 2, 2},
        {4, 3, 3}
    };

    // 初始化分配矩阵
    int alloc[NUM_PROCESSES][NUM_RESOURCES] = {
        {0, 1, 0},
        {2, 0, 0},
        {3, 0, 2},
        {2, 1, 1},
        {0, 0, 2}
    };

    // 复制到全局变量
    for (int i = 0; i < NUM_PROCESSES; i++) {
        for (int j = 0; j < NUM_RESOURCES; j++) {
            maximum[i][j] = max[i][j];
            allocation[i][j] = alloc[i][j];
            need[i][j] = maximum[i][j] - allocation[i][j];
        }
    }
}

步骤三：检查系统是否处于安全状态

c
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bool isSafeState() {
    int work[NUM_RESOURCES];
    bool finish[NUM_PROCESSES] = {false};
    int safeSequence[NUM_PROCESSES];
    int count = 0;

    for (int i = 0; i < NUM_RESOURCES; i++) {
        work[i] = available[i];
    }

    while (count < NUM_PROCESSES) {
        bool found = false;
        for (int p = 0; p < NUM_PROCESSES; p++) {
            if (!finish[p]) {
                int j;
                for (j = 0; j < NUM_RESOURCES; j++) {
                    if (need[p][j] > work[j]) {
                        break;
                    }
                }

                if (j == NUM_RESOURCES) {
                    for (int k = 0; k < NUM_RESOURCES; k++) {
                        work[k] += allocation[p][k];
                    }
                    safeSequence[count++] = p;
                    finish[p] = true;
                    found = true;
                }
            }
        }

        if (!found) {
            return false;
        }
    }

    printf("System is in a safe state.\nSafe sequence is: ");
    for (int i = 0; i < NUM_PROCESSES; i++) {
        printf("%d ", safeSequence[i]);
    }
    printf("\n");
    return true;
}

步骤四：处理资源请求

c
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bool requestResources(int process_id, int request[]) {
    for (int i = 0; i < NUM_RESOURCES; i++) {
        if (request[i] > need[process_id][i]) {
            printf("Error: Process has exceeded its maximum claim.\n");
            return false;
        }
    }

    for (int i = 0; i < NUM_RESOURCES; i++)