Question: Count how many times a loop is executed.

[NewProgramma]

Hello everyone,

I have a question regarding a "counter" inside a nested "for loop", and use this counter to count how many times the loop has been executed. Below is an example code:

-----------------------------------------
for ( x = 0; x < 10; x++)
{
for (y = 0; y < 5; y++)
{
counter1++;
}
couter2++;
}
cout << couter1 << " " << counter2;
-----------------------------------------

Accourding to my understanding, the total amount executed for the nested "for loop" should be 50 times (10 * 5 = 10 outer loops * 5 nested loops( for each outer loops) ), but how come the output for "counter1" is 98?...did I miss place this counter?

Thank you all for the generous help.

[MiiNiPaa]

How counter1 is declared? Show full code.

[NewProgramma]

here is the full code:


------------------------------------------------

#include <iostream>
using namespace std;


int main()
{
int x, y, counter1, counter2;

for (x = 0; x < 10; x++)
{
for (y = 0; y < 5; y++)
{
counter1++;
}
counter2++;
}

cout << counter1 << "," << counter2;

return 0;
}

------------------------------------------------

output: 98,10


ummm........when I change the test expressions "x < 10 and y < 5" to "x < 5 and y < 2" the counter1 outputs 58 lol.......I got no idea what the error is.

[MiiNiPaa]

counter1 is indeed incremented 50 times. So you can rewrite your code as:

int counter1;
counter1 = counter1  + 50;
std:cout << counter1;

Now tell, what is the value of counter1? What counter1 + 50 means and how it calculated?

[NewProgramma]

hmmm, I've modified the program based on your insight, and counter1 turned out to be 50:

int x, y, counter1 = 0, counter2;

for (x = 0; x < 10; x++)
{
for (y = 0; y < 5; y++)
{
counter1 += 1;
}
counter2++;
}
cout << counter1;

but, i'm still curious as to why using "counter2++" worked while "counter1++"
isn't outputting the correct number.

And, when I initialize "counter1 = 0"; using "counter1++" worked correctly and outputted 50 xD.....I guess it's the initialization part.......bah I'm so lost here lol.

[MiiNiPaa]

why using "counter2++" worked

Two people were running the red light. One reached the other side, second got hit by a car. Why?

Using uninitialized variable is undefined behavior. You just happened to get correct result. On your next run, or when you change your program, or when you reboot your PC, or when you upgrade your compiler, or in any of thousand of possibilities you can get wrong result.
You should never use uninitialized variables.

Also it is a good idea to declare loop counters inside loop itself:

int counter_inner = 0;
int counter_outer = 0;
for(int x = 0; x < 10; ++x) {
    for(int y = 0; y < 5; ++y)
        ++counter_inner;
    ++counter_outer;
}
std::cout << counter_inner << "; " << counter_outer << '\n';

[NewProgramma]

I see. I really need to get in the habit of initializing variables haha. Thank you very much for the help.