Function generates random number in array

Question

I am trying to create a function that creates random number for a array. Here is my code.

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

#define ROW 22
#define COL 80


void display(int life[ROW][COL]){
    for(int i = 0; i<ROW; i++){
        for(int j=0; j<COL; j++){
            printf("%d",life[i][j]);
        }
        printf("\n");
    }
}
void initialize_board(int life[ROW][COL]){
    for(int i = 0; i< ROW;i++){
        for(int j = 0; j<COL ; j++){
            life[ROW][COL] = rand()%2;
        }
    }
}
int main() {
    srand(getpid());
    printf("PID: %d\n",getpid());
    int life[22][80] = {0};
    initialize_board(life);
    display(life);
    return 0;
}

However I got output are 0s not randomly assigned to 0 or 1.

Ivaylo Valchev · Accepted Answer · 2018-05-08 06:44:20Z

5

Instead of

life[ROW][COL] = rand()%2;

use

life[i][j] = rand()%2;

inside that loop.

As it stands, you're writing all random values to the same (invalid) memory address a bit behind the end of the array.

edited May 8, 2018 at 6:44

Ivaylo Valchev

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answered May 8, 2018 at 6:35

Wintermute

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2 Comments

Yunnosch Over a year ago

@Akrios Be more polite to people, including yourself.

Wintermute Over a year ago

Rest assured that there's not one among us who hasn't made similar mistakes before. Except those who are just starting out and haven't written any code yet; they will make them in the future. :P

Mike · Accepted Answer · 2018-05-08 07:24:31Z

0

[ROW][COL] are constanst, so you're writing always in the same (invalid, as Wintermute mentioned) cell. So you had to use the variables i and j kind regards

answered May 8, 2018 at 7:24

Mike

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