My increment doesn't work (c) - c

Question

So, I have this code, at end I have an increment for exit when it reaches 4 (4 times wrong value entered), but it doesn't work:
int main() {
int nej;
printf("1-Triangulo \n");
printf("2-Division \n");
printf("3-Menu \n");
printf("4-Bosque \n");
printf("0-Salir \n");
scanf("%d", &nej);
if (nej == 1) {
// Ejercicio 1-Triangulo:
triangulo();
}
if (nej == 2) {
// Ejercicio 2-Division:
division();
}
if (nej == 3) {
menu();
}
if (nej == 4) {
arboles();
}
if (nej == 0) {
// Salida
exit(1);
}
int nerr = 0;
while (nej < 0 || nej > 4) {
nerr++;
// Contador de error
if (nerr == 4) {
exit(1);
}
}
}
How to fix this?

Answer 1

I believe you have a typo inside the while condition
while (nej < 0 || nej > 4) {
...
should be:
while (nerr < 0 || nerr > 4) {
..

Answer 2

nej being the input, and the input being invalid if less than 0 or larger than 4, the correct statement would be:
if (nej < 0 || nej > 4) {
(and not while as nej is not changed in the code block).

Answer 3

If you initialize the int nerr = 0; every time when you read,the flow will never reach the exit condition
int main()
{
int nej;
int nerr = 0; // Keep the counter outside the loop
while (true){//Start a infinite loop here
printf("1-Triangulo \n");
printf("2-Division \n");
printf("3-Menu \n");
printf("4-Bosque \n");
printf("0-Salir \n");
scanf("%d", &nej);
if (nej == 1) {
// Ejercicio 1-Triangulo:
triangulo();
}
if (nej == 2) {
// Ejercicio 2-Division:
division();
}
if (nej == 3) {
menu();
}
if (nej == 4) {
arboles();
}
if (nej == 0) {
// Salida
exit(1);
}
while (nej < 0 || nej > 4) {
nerr++;
// Contador de error
if (nerr == 4) {
exit(1);
}
}
}

Answer 4

It have following errors:
Code should be in the while loop
Variable nerr should be declared and initialize outside the while loop
Variable nerr should control the while loop
Note: It is Ok to use multiple if. But use of switch is much convenient and advisable.
Corrected code is as following:
int main() {
int nej;
int nerr = 0;
while (nerr < 4) {
printf("1-Triangulo \n");
printf("2-Division \n");
printf("3-Menu \n");
printf("4-Bosque \n");
printf("0-Salir \n");
scanf("%d", &nej);
switch(nej){
case 1:// Ejercicio 1-Triangulo:
triangulo();
break;
case 2:// Ejercicio 2-Division:
division();
break;
case 3:
menu();
break;
case 4:
arboles();
break;
case 0:// Salida
exit(1);
break;
default:
nerr++;
}
// Reset 'nerr' if any valid vaue is entered by user
if ((nej >= 0) && (nej <= 4)) {
nerr = 0;
}
}
}