C++ christmas tree - c++

Question

I've just started learning C++ and decided to give myself a challenge by creating a simple Christmas Tree program. Everything has been working so far although the code doesn't produce what I expect. I've spent a decent amount of time trying to figure out what's wrong but can't seem to figure out why it doesn't work.
So far, the code looks like this:
#include <iostream>
#include <string>
int main(){
char cTree;
int iSize, iSpace;
std::cout << "Christmas Tree Application" << std::endl;
std::cout << "Enter the size of your christmas tree: ";
std::cin >> iSize;
std::cout << "Enter the character you would like to use for your tree: ";
std::cin >> cTree;
iSpace = iSize / 2;
for(int i = 0; i < iSize; i++){
std::string sTree(i, cTree);
//std::string sSpace(iSpace, ' ');
std::cout << sTree << std::endl;
//iSpace -= 1;
}
return 0;
}
I've also commented out the 'spacing' part because whenever I execute it, it creates an error that I have no clue why it is says that. I know I can do the spacings in a different manner but I'd like to use the std::string way. Any help?

Answer 1

iSpace is set to iSize / 2, yet you run the loop iSize times, decreasing iSpace by one every time. Eventually, iSpace will be negative, which is why you have the error. Try this:
iSpace = iSize;
for(int i = 0; i < iSize; i++){
std::string sTree(i, cTree);
std::string sSpace(iSpace, ' ');
std::cout << sSpace << sTree << sTree << std::endl;
iSpace -= 1;
}

Answer 2

You are looping on the wrong value for iSpace, as it remains constant throughout execution rather than changing like a variable does.
Also, your code can be tidied up a bit. I've posted the updated code below. I've deliberately replaced spaces with underscore characters to provide a better graphical representation of my logic.
Good luck!
Code Listing
#include <iostream>
#include <string>
using namespace std;
int main(void) {
char cTree;
int iSize;
int iSpace;
int iChars;
cout << "Christmas Tree Application" << endl;
cout << "Enter the height of your christmas tree: ";
cin >> iSize;
cout << "Enter the character you would like to use for your tree: ";
cin >> cTree;
for(int i = 0; i < iSize; i++){
iSpace = (iSize-i)-1;
iChars = (2*i)+1;
string sSpace(iSpace, '_');
string sTree(iChars, cTree);
cout << sSpace << sTree << sSpace << endl;
}
return 0;
}
Sample Run
Christmas Tree Application
Enter the height of your christmas tree: 10
Enter the character you would like to use for your tree: #
_________#_________
________###________
_______#####_______
______#######______
_____#########_____
____###########____
___#############___
__###############__
_#################_
###################

Answer 3

awesomeyi is right about the error, however if you'd like it to look more "tree-like" you'll need to double your loop.
i.e.
#include <iostream>
#include <string>
int main(){
char cTree;
int iSize, iSpace;
std::cout << "Christmas Tree Application" << std::endl;
std::cout << "Enter the size of your christmas tree: ";
std::cin >> iSize;
std::cout << "Enter the character you would like to use for your tree: ";
std::cin >> cTree;
iSpace = iSize;
for (int i = 0; i < iSize*2; i+=2){
std::string sTree(i, cTree);
std::string sSpace(iSpace, ' ');
std::cout << sSpace + sTree + sSpace<< std::endl;
iSpace -= 1;
}
return 0;
}

Answer 4

Just for fun, here's a recursive implementation:
#include <iostream>
#include <string>
#include <cstdio>
void drawTree(int level, int height, char c) {
if(level > 0)
drawTree(level-1, height, c);
std::cout << std::string(height-level, ' ') << std::string((2*level)+1, c) << std::endl;
}
int main(){
char cTree;
int iSize;
std::cout << "Christmas Tree Application" << std::endl;
std::cout << "Enter the size of your christmas tree: ";
std::cin >> iSize;
std::cout << "Enter the character you would like to use for your tree: ";
std::cin >> cTree;
drawTree(iSize, iSize, cTree);
return 0;
}