Why star pattern work with one code and doesn't work with another code? Logic is same

I’m trying to solve Star problem. And I always thought it’s good practice not to declare empty variable in the beginning.

when I declare variables and assign some value at the beginning it doesn’t work
here is the code where i=1,j=1,space=1

#include<stdio.h>
int main()
{
    int i=1,space=1,j=1,rows;
    printf("Enter number of rows: ");
    scanf("%d",&rows);
    for(i;i<=rows;i++)
    {
        for(space;space<=rows-i;space++)
    {
        printf(" ");
    }
    for(j;j<=2*i-1;j++)
    {
        printf("*");
    }
    printf("\n");
    }
    return 0;
}

BUT when I only declare variables and assign value in for loop it does work

#include<stdio.h>
int main()
{
    int i,space,j,rows;
    printf("Enter number of rows: ");
    scanf("%d",&rows);
    for(i=1;i<=rows;i++)
    {
        for(space=1;space<=rows-i;space++)
        {
            printf(" ");
        }
        for(j=1;j<=2*i-1;j++)
        {
            printf("*");
        }
        printf("\n");
    }
    return 0;
}

Why it’s happening? I always thought it’s a good practice to declare variables and assign some value to them

>Solution :

In first case space and j doesn’t reinit in parent for loop, while in the second example every parent loop iteration you reassign j = 1 and space = 1
So, on start of second iteration j and space will be the same as were on the finish of first iteration, so nested loops won’t work