Making Ludo using Semaphores. 4 processes running sequentially like round robin - c

Question

During this lockdown period, you are playing Ludo with your n number of family members where, n<=4. Assume that all the tokens are in the starting square and consider following scenarios: If the outcome of the dice is 6(six), then you can move your one token and get the chance to play dice again; otherwise, you can move your one token and give the dice to the next
player. Think of the players as processes which should be synchronized. You are
required to write a code for it using semaphore.
What I've tried is:
#include <stdio.h>
#include <stdlib.h>
#include <pthread.h>
#include <semaphore.h>
sem_t *S;
pthread_mutex_t mutex;
int *play, n;
void check(int pid) {
six:
int num = (rand() % 6) + 1;
printf("Player %d rolled and got %d\n", pid + 1, num);
if(num == 6) goto six;
sem_post(&S[pid]); //only for next()
}
void roll(int pid) {
pthread_mutex_lock(&mutex);
check(pid);
pthread_mutex_unlock(&mutex);
sem_wait(&S[pid]);
}
void next(int pid) {
pthread_mutex_lock(&mutex);
int next = (pid+1)%n;
printf("Player %d passed the die to %d\n", pid + 1, next + 1);
check(next);
pthread_mutex_unlock(&mutex);
}
void *player(void *num) {
for (int i = 0; i < n; i++) {
roll(*((int *)num));
next(*((int *)num));
}
}
int main() {
printf("Enter No. of players : ");
scanf("%d",&n);
pthread_t pid[n];
pthread_mutex_init(&mutex, NULL);
S = malloc(n*sizeof(sem_t));
play = malloc(n*sizeof(int));
for(int i = 0; i < n; i++){
play[i] = i;
sem_init(&S[i], 0, 0);
}
for (int i = 0; i < n; i++)
pthread_create(&pid[i], NULL, player, &play[i]);
for (int i = 0; i < n; i++)
pthread_join(pid[i], NULL);
pthread_mutex_destroy(&mutex);
for (int i = 0; i < n; i++)
sem_destroy(&S[i]);
return 0;
}```
This is the output : https://i.stack.imgur.com/ZaNUC.png
I want to rectify the sequence by making the one rolling person is the one whom the die is passed.