Get Pi by Monte Carlo method.

pi_MonteCarlo.c

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

unsigned int next;
unsigned int A = 1103515245, C = 12345, M = 2147482648;

double my_rand(void){
   
    next = (next * A + C) % M;
    return next;
}

void my_srand(unsigned int seed){
    next = seed;
}

int main(int argc, char *argv[]){
    int i, n, k;
    double x, y, pi;
    n = atoi(argv[1]);
    k = 0;

    my_srand((unsigned)time(NULL));
    for(i=0; i<n; i++){
       x = my_rand()/(M-1);
       y = my_rand()/(M-1);
    
       if(x*x + y*y <= 1){
            k++;
       }
    } 
   
    pi = (double)4*k/n;
    printf("pi = %lf\n", pi);

    return 0;
}