用c语言编写一个银行家算法

银行家算法是一种资源分配算法，用于避免死锁的产生。以下是用C语言实现银行家算法的代码示例：

#include <stdio.h>
#include <stdlib.h>

#define MAX_PROCESS 10
#define MAX_RESOURCE 10

int available[MAX_RESOURCE];
int max[MAX_PROCESS][MAX_RESOURCE];
int allocation[MAX_PROCESS][MAX_RESOURCE];
int need[MAX_PROCESS][MAX_RESOURCE];
int finish[MAX_PROCESS] = {0};
int safe_sequence[MAX_PROCESS];
int num_processes, num_resources;

void input()
{
    int i, j;

    printf("Enter number of processes: ");
    scanf("%d", &num_processes);

    printf("Enter number of resources: ");
    scanf("%d", &num_resources);

    printf("Enter available resources: ");
    for (i = 0; i < num_resources; i++) {
        scanf("%d", &available[i]);
    }

    printf("Enter maximum resources needed by each process:\n");
    for (i = 0; i < num_processes; i++) {
        printf("Process %d: ", i);
        for (j = 0; j < num_resources; j++) {
            scanf("%d", &max[i][j]);
        }
    }

    printf("Enter resources allocated to each process:\n");
    for (i = 0; i < num_processes; i++) {
        printf("Process %d: ", i);
        for (j = 0; j < num_resources; j++) {
            scanf("%d", &allocation[i][j]);
            need[i][j] = max[i][j] - allocation[i][j];
        }
    }
}

int safety_check()
{
    int i, j, k, count = 0, safe = 0;

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

    while (count < num_processes) {
        safe = 0;
        for (i = 0; i < num_processes; i++) {
            if (finish[i] == 0) {
                int flag = 1;
                for (j = 0; j < num_resources; j++) {
                    if (need[i][j] > work[j]) {
                        flag = 0;
                        break;
                    }
                }
                if (flag) {
                    for (j = 0; j < num_resources; j++) {
                        work[j] += allocation[i][j];
                    }
                    finish[i] = 1;
                    safe_sequence[count++] = i;
                    safe = 1;
                }
            }
        }
        if (!safe) {
            break;
        }
    }

    if (count == num_processes) {
        printf("Safe sequence: ");
        for (i = 0; i < num_processes; i++) {
            printf("%d ", safe_sequence[i]);
        }
        printf("\n");
        return 1;
    } else {
        printf("System is in unsafe state.\n");
        return 0;
    }
}

int request_resources(int pid, int *request)
{
    int i, j, safe = 0;

    for (i = 0; i < num_resources; i++) {
        if (request[i] > need[pid][i] || request[i] > available[i]) {
            printf("Error: Requested resources exceed max or available.\n");
            return 0;
        }
    }

    for (i = 0; i < num_resources; i++) {
        available[i] -= request[i];
        allocation[pid][i] += request[i];
        need[pid][i] -= request[i];
    }

    if (safety_check()) {
        printf("System is in safe state.\n");
        safe = 1;
    } else {
        printf("System is in unsafe state, rolling back.\n");
        for (i = 0; i < num_resources; i++) {
            available[i] += request[i];
            allocation[pid][i] -= request[i];
            need[pid][i] += request[i];
        }
    }

    return safe;
}

int release_resources(int pid, int *release)
{
    int i;

    for (i = 0; i < num_resources; i++) {
        if (release[i] > allocation[pid][i]) {
            printf("Error: Released resources exceed allocated.\n");
            return 0;
        }
    }

    for (i = 0; i < num_resources; i++) {
        available[i] += release[i];
        allocation[pid][i] -= release[i];
        need[pid][i] += release[i];
    }

    return 1;
}

int main()
{
    int i, j, pid;
    int request[MAX_RESOURCE], release[MAX_RESOURCE];

    input();

    safety_check();

    while (1) {
        printf("Enter process ID (or -1 to exit): ");
        scanf("%d", &pid);

        if (pid == -1) {
            break;
        }

        printf("Enter request: ");
        for (i = 0; i < num_resources; i++) {
            scanf("%d", &request[i]);
        }

        if (request_resources(pid, request)) {
            printf("Resources allocated.\n");
        } else {
            printf("Resources not allocated.\n");
        }

        printf("Enter release: ");
        for (i = 0; i < num_resources; i++) {
            scanf("%d", &release[i]);
        }

        if (release_resources(pid, release)) {
            printf("Resources released.\n");
        } else {
            printf("Resources not released.\n");
        }

        printf("Available resources: ");
        for (i = 0; i < num_resources; i++) {
            printf("%d ", available[i]);
        }
        printf("\n");

        printf("Allocation:\n");
        for (i = 0; i < num_processes; i++) {
            for (j = 0; j < num_resources; j++) {
                printf("%d ", allocation[i][j]);
            }
            printf("\n");
        }

        printf("Need:\n");
        for (i = 0; i < num_processes; i++) {
            for (j = 0; j < num_resources; j++) {
                printf("%d ", need[i][j]);
            }
            printf("\n");
        }
    }

    return 0;
}