Why is my nailboard experiment not working? - c

Question

I wanted to simulate the distribution of n balls which fall on a nailboard with j rows into rows+1 cups. You see, the code is simpel. There are two inputs and an array which is called faecher which contains the cups. For every ball and row 0 or 1 is radnomly chosen. With this in mind I can calculate the cup. At the end it should vertically print as many # as there are balls in a cup. However it does not function properly. It does not matter which amount of balls I input it always prints just two #.
int main(int argc, const char *argv[])
{
int kugel = atoi(argv[1]);
int reihe = atoi(argv[2]);
int zahl;
int faecher[reihe+1];
for(int i=0;i <=reihe;i++){
faecher[i]= 0;
}
for(int j = 1;j <= kugel;j++ ){
for(int i = 0; i < reihe; i++){
zahl = rand()%2;
}
faecher[zahl]+= 1;
}
for(int j=0;j <=reihe;j++){
for(int i=1;i<=faecher[j];i++){
printf("#");
}
printf("\n");
}
return 0;
}
I was expecting an exact amount of #.

Answer 1

zahl = rand()%2; just sets the column the ball will fall into to 0 or 1. What you want to do is mimic the ball moving left or right at each pin. To do that, you can use zahl += rand() % 2;. However, you need to initialize zahl to 0 for each row. So remove the current int zahl; declaration and, after inside the loop on j, insert int zahl = 0;:
#include <stdio.h>
#include <stdlib.h>
int main(int argc, const char *argv[])
{
int kugel = atoi(argv[1]);
int reihe = atoi(argv[2]);
// Deleted line: int zahl;
int faecher[reihe+1];
for(int i=0;i <=reihe;i++){
faecher[i]= 0;
}
for(int j = 1;j <= kugel;j++ ){
int zahl = 0; // New line.
for(int i = 0; i < reihe; i++){
zahl += rand()%2; // Changed line.
}
faecher[zahl]+= 1;
}
for(int j=0;j <=reihe;j++){
for(int i=1;i<=faecher[j];i++){
printf("#");
}
printf("\n");
}
return 0;
}
Then, for 300 balls and 10 rows, you may get an output like:
#
###########
##############################
#############################################################
####################################################################
######################################################################
########################################
###############
####