If statement to control range of numbers using array - c++

Question

I have created an array that holds 5 numbers, and the user inputs the numbers. If the mark is less than 0 and greater than 100, I want to print out "invalid mark number". How could I do that?
using namespace std;
int mark[5];
int main ()
{
cout << "enter mark 0: ";
cin >> mark[0];
cout << "enter mark 1: ";
cin >> mark[1];
cout << "enter mark 2: ";
cin >> mark[2];
cout << "enter mark 3: ";
cin >> mark[3];
cout << "enter mark 4: ";
cin >> mark[4];
}

Answer 1

You should use a for-loop to make the code more readable and compact. Because once you introduce if statements, the code size would grow alot. It should look like this:
#include <iostream>
using namespace std;
int mark[5];
int main () {
for (int i = 0; i < 5; i++){
cout << "enter mark " << i << ": ";
cin >> mark[i];
if (mark[i] < 0 || mark[i] > 100){
cout << "invalid mark number\n";
}
}
}
Don't use using namespace std; (read here why) and keep the int mark[5]; inside the main-function (read here why). Also to add to the logic force the user to input again:
#include <iostream>
int main () {
int mark[5];
for (int i = 0; i < 5; i++){
bool valid_input = false;
while (!valid_input){
std::cout << "enter mark " << i << ": ";
std::cin >> mark[i];
if (mark[i] < 0 || mark[i] > 100){
std::cout << "invalid mark number\n";
}
else{
valid_input = true;
}
}
}
}