Nested For loop to Do while Loop - c++

Question

Hi I read the guidelines about homework questions and it says to clearly state that it is homework. This is homework, I have spent the last 45 minutes trying over and over again. I've hit a wall and need help.
My assignment was to take this code that came from a double For loop and convert it into a while loop nested into a for loop. I have successfully completed that. However, the 3rd part is to take that code and make the outer for loop into a do while loop.
The output needs to increment a "#" each line like so if the input was "4"
#
##
###
####
Below is my code that I wrote that I need to make the outer for loop into a do while loop:
int main()
{
int side;
cout << "Enter a number: ";
cin >> side;
for (int i = 0; i < side; i++)
{
int j = i;
while(j >= 0)
{
cout << "#";
j--;
}
cout << "\n";
}
}
This is my attempt so far:
int main()
{
int side;
int i;
cout << "Enter a number: ";
cin >> side;
int j=side;
do
{
while(j >= 0)
{
cout << "#";
j--;
}
cout << "\n";
i++;
}
while(j >= side);
}
My teacher said as long as the code is explained and I understand how it works that it's okay. Any help would be much appreciated.
Thanks.

Answer 1

The first mistake you made is this:
int i; //not initialized!
/*...*/
i++;
and you didn't even use it in your do-while condition.
So while(j >= side); > while (i >= side);
Actually, that's not true, either. Since side is the input, you want i to check if it's smaller not greater then the input. So it's while (i < side);
Another thing is int j=side;, when you decrement j it will never reset, so you must set this into your do-while loop and also initialize it with i rather than side....
Anyway, here's the full code:
#include <iostream>
using namespace std;
int main()
{
int side;
int i = 0;
cout << "Enter a number: ";
cin >> side;
do
{
int j = i;
while (j >= 0)
{
cout << "#";
j--;
}
cout << "\n";
i++;
} while (i < side);
return 0;
}
example output:
Enter a number: 10
#
##
###
####
#####
######
#######
########
#########
##########

Answer 2

I suggest
int main()
{
int side;
int i = 0;
cout << "Enter a number: ";
cin >> side;
do
{
int j = i;
while(j >= 0)
{
cout << "#";
j--;
}
cout << "\n";
i++;
}while(i < side)
}
A for loop usually consists in an initialization (i=0), a stop condition (i < side) and an increment (i++); why would you not use i anymore?

Answer 3

while(j >= side); should be while(i <= side);
j should be initialized in each iteration of the outer loop (j = i;)
int j=side; is unnecessary.
An friendly suggestion - name your variables and functions descriptively - row and column are much better than i and j.

Answer 4

They answer above solves your problem but let me show you a shorter way to do things:
int main()
{
int side;
std::cout << "Enter a number: ";
std::cin >> side;
int row = 1;
do
{
int col = 0;
while (col++ != row)
{
std::cout << "#";
}
std::cout << "\n";
} while (row++ != side); //This way, the condition is checked (row != side), and then row is incremented
}