Miscalculation with While

Question

In this exercise it is to type two numbers and print on the screen themselves, and the integers between them. However, if I type for example 10 and 20, the last number that appears is 19 instead of 20; and if I type 20 and 10, the last number appears 11.

My mistake is not in ifFor what I have tested, I may be wrong.

NOTE: I need to use while.

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

int n1, n2;

main()
{
    printf("Para saber os inteiros entre dois numeros siga os passos abaixo: \n");
    printf("Digite o primeiro numero: ");
    scanf("%d", &n1);
    printf("Digite o segundo numero: ");
    scanf("%d", &n2);
    system("cls");
    if((n1 == n2)||(n2 == n1)){
            printf("NUMEROS IGUAIS!\n");
    }
    while((n1 < n2)||(n1 > n2))
    {
         if(n1 < n2){
            printf("%d\n", n1);
            n1 = n1 + 1;
        }else if(n1 > n2){
            printf("%d\n", n1);
            n1 = n1 - 1;
        }
    }
    return 0;
}

Answer 1

The main problem is that it is stopping when it is larger or smaller, but you want to include the value within the limit, so you have to accept when the value is equal to the limit too so you would need to use r <= and >= in the while.

This code is too complex and inefficient to do several operations without any need (3 branches in each step against 1 of mine). So I think it best to do so:

#include <stdio.h>

int main() {
    int n1, n2;
    printf("Para saber os inteiros entre dois numeros siga os passos abaixo: \n");
    printf("Digite o primeiro numero: ");
    scanf("%d", &n1);
    printf("Digite o segundo numero: ");
    scanf("%d", &n2);
    if (n1 == n2) printf("NUMEROS IGUAIS!\n");
    else if (n1 < n2) while (n1 <= n2) printf("%d\n", n1++);
    else while (n1 >= n2) printf("%d\n", n1--);
}

Behold working in the ideone. And in the repl it.. Also put on the Github for future reference.

Answer 2

Use the operator <= in your condition, like:

do {
     if(n1 <= n2){
       printf("%d\n", n1);
       n1 = n1 + 1;
     } else {
       printf("%d\n", n1);
       n1 = n1 - 1;
     }
 } while((n1 <= n2)||(n1 => n2));