使用C语言给出银行家算法代码
时间: 2023-11-03 21:04:56 浏览: 22
Sure, here is an example implementation of the Banker's Algorithm in C language:
```
#include <stdio.h>
#include <stdbool.h>
#define MAX_RESOURCES 5
int available[MAX_RESOURCES];
int allocation[MAX_RESOURCES][MAX_RESOURCES];
int max[MAX_RESOURCES][MAX_RESOURCES];
int need[MAX_RESOURCES][MAX_RESOURCES];
bool check_safety();
int main() {
// initialize available resources
for (int i = 0; i < MAX_RESOURCES; i++) {
printf("Enter the number of available instances for resource %d: ", i);
scanf("%d", &available[i]);
}
// initialize allocation matrix
for (int i = 0; i < MAX_RESOURCES; i++) {
for (int j = 0; j < MAX_RESOURCES; j++) {
allocation[i][j] = 0;
}
}
// initialize max matrix
for (int i = 0; i < MAX_RESOURCES; i++) {
printf("Enter the maximum demand for resource %d: ", i);
for (int j = 0; j < MAX_RESOURCES; j++) {
scanf("%d", &max[i][j]);
}
}
// calculate need matrix
for (int i = 0; i < MAX_RESOURCES; i++) {
for (int j = 0; j < MAX_RESOURCES; j++) {
need[i][j] = max[i][j] - allocation[i][j];
}
}
// check safety before starting resource allocation
if (check_safety()) {
printf("System is safe, proceeding with resource allocation\n");
} else {
printf("System is not safe, cannot proceed with resource allocation\n");
return 0;
}
// read the process ID and request vector
int pid;
int req[MAX_RESOURCES];
printf("Enter process ID: ");
scanf("%d", &pid);
printf("Enter request vector: ");
for (int i = 0; i < MAX_RESOURCES; i++) {
scanf("%d", &req[i]);
}
// check if the request can be granted
bool is_granted = true;
for (int i = 0; i < MAX_RESOURCES; i++) {
if (req[i] > need[pid][i]) {
is_granted = false;
break;
}
if (req[i] > available[i]) {
is_granted = false;
break;
}
}
// grant the request and update state
if (is_granted) {
for (int i = 0; i < MAX_RESOURCES; i++) {
available[i] -= req[i];
allocation[pid][i] += req[i];
need[pid][i] -= req[i];
}
// check safety after resource allocation
if (check_safety()) {
printf("Request granted, system is safe\n");
} else {
printf("Request granted, but system is not safe\n");
}
} else {
printf("Request cannot be granted\n");
}
return 0;
}
bool check_safety() {
int work[MAX_RESOURCES];
bool finish[MAX_RESOURCES];
// initialize work and finish arrays
for (int i = 0; i < MAX_RESOURCES; i++) {
work[i] = available[i];
finish[i] = false;
}
// check if there is a process that can be finished
bool can_finish = true;
while (can_finish) {
can_finish = false;
for (int i = 0; i < MAX_RESOURCES; i++) {
// skip finished and already checked processes
if (finish[i] || need[i][0] == -1) continue;
// check if the current process can be finished
bool can_be_finished = true;
for (int j = 0; j < MAX_RESOURCES; j++) {
if (need[i][j] > work[j]) {
can_be_finished = false;
break;
}
}
// if the current process can be finished
if (can_be_finished) {
// release allocated resources and update work
for (int j = 0; j < MAX_RESOURCES; j++) {
work[j] += allocation[i][j];
}
// mark process as finished
finish[i] = true;
can_finish = true;
}
}
}
// if all processes are finished, the system is safe
for (int i = 0; i < MAX_RESOURCES; i++) {
if (!finish[i]) {
return false;
}
}
return true;
}
```
You can modify this implementation according to your specific requirements.