How to display integers with pattern using loop? - c

Question

I'm trying to display the integer like
1111
222
33
4
using loop but i dont know what is wrong with my code, i'm new to c programming and thanks for your help :D
Here is my code :
#include <stdio.h>
int main()
{
int a, b;
for (int a=4; a<=1; a--)
{
for (int b=1; b<=a; b++) {
printf("%d", b);
}
}
printf("\n");
}

Answer 1

What is wrong:
#include <stdio.h>
int main()
{
int a, b;
for (int a=4; a<=1; a--) /* a<=1 is false when a=4 */
{
for (int b=1; b<=a; b++) {
printf("%d", b); /* what is printed depends on b while it shouldn't */
}
}
printf("\n"); /* this is in wrong place */
}
Fixed code:
#include <stdio.h>
int main()
{
int a, b;
for (int a=4; a>=1; a--)
{
for (int b=1; b<=a; b++) {
printf("%d", 1 + (4 - a));
}
printf("\n");
}
}

Answer 2

First, the condition in the first loop "a<=1" will never be true since you are initializing a=4.

Answer 3

for (int a=4; a<=1; a--)
it will get out of the loop in the first iteration as a=4 and 4 is not less then 1
one of the way to print this is....
#include <stdio.h>
int main()
{
int a, b;
for (a=1; a<=4; a++)
{
for (b=4; b<=1; b--) {
printf("%d", a);
}
}
printf("\n");
printf("Hello, World!\n");
return 0;
}

Answer 4

Your code has four issues.
1.
You declare a and b twice. One time before and one time inside of the loops. The ones you use are actually the variables you declare/define inside of the loop's initialization parts. The variables a and b declared outside are completely redundant and unused in your actual code.
2.
The condition of the outer for loop a <= 1 will never be true and you will not at least go one time through the loops because a is initialized with 4 and since 4 is not less or equal than 1 you will have no iteration at all.
The condition needs to be a >= 1, not a <= 1.
3.
printf("\n"); needs to be placed inside of the outer loop and not outside of it.
4.
The logic of your inner for loop is flaw. We need a counter inside of the inner loop and test it against a condition instead to use and increment b. Doing so would gives you only numbers in ascending order in each line.
Increment b after the inner loop is complete.
Corrected code (Online test):
#include <stdio.h>
int main (void)
{
int a = 4, b = 1;
for ( ; a >= 1; a-- ) {
for ( int i = 0; i < a; i++ ) {
printf("%d", b);
}
b++;
printf("\n");
}
}
Execution:
./a.out
1111
222
33
4