When I print all the variables of a list it gives me an unexpected value that is inconsistent in c. Can you tell me what went wrong?

Question

Here is the code

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

struct rule {
    int id;
    int allow[3];
};

char key_id[10] = { '\\', '/', '`', '#', '_', '*', '@', '%', '>', '<' };

struct rule def_rule(int id, int *arr, int arr_size) {
    struct rule temp;
    temp.id = id;
    for (int i; i < arr_size; i++) {
        temp.allow[i] = arr[i];
    }
    return temp;
}

void collapse(int *map, int map_w, int map_h) {
    srand(time(0));
    //finding adj indexes
    int nth;
    int wst;
    int sth;
    int est;
    int map_a = map_h * map_w;
    int dir[4] = { nth, wst, sth, est };
    for (int i = 0; i < map_w * map_h; i++) {
        if ((i - 4) >= 0) {
            nth = map[i - 4];
        }

        if ((i + 1) < map_a) {
            wst = map[i + 1];
        }

        if (i + 4 <= 15) {
            sth = map[i + 4];
        }

        if (i - 1 >= 0) {
            est = map[i - 1];
        }
    }
}


void main(void) {
    //define some rules
    struct rule rules[0];
    int arr[3] = { 0, 1, 2 };
    rules[0] = def_rule(0, arr, 3);

    //collapse
    int map_w = 4;
    int map_h = 4;
    int map[map_w * map_h];
    for(int i = 0; i < 15; i++) {
        map[i] = 0;
    }
    collapse(map, map_w, map_h);
    for (int i = 0; i < map_w; i++) {
        for (int j = 0; j < map_h; j++) {
            printf(" %d ", map[(i * 4) + j]);
        }
        printf("\n");
    }
}

When I compile it it doesn't give me any errors or warnings and I think when I access map[i] I am not out of range. However it gives me this output in my terminal:

 0  0  0  0 
 0  0  0  0 
 0  0  0  0 
 0  0  0  21896

When I run it again 21896 changes to a different number.

I am trying to turn zeros in an array into other numbers depending on some rules. I made the code for checking adjacency such that it doesn't change the variable map. The only time variable map is changed is when I iterate over it to set everything to 0. I have tested all the code and it seemed to work however when I added structs it started to do this.

Edit:

The problem was that I was accessing all but the last index of map so I was trying to print an undefined variable I think.

Answer 1

The initialization loop for map is incorrect: you never initialize the last element. You should use:

    int map[map_w * map_h];
    for (int i = 0; i < map_w * map_h; i++) {
        map[i] = 0;
    }