### How to print a triangle using user-defined coordinates?

I have to write a program that takes three sets of user-given coordinates (x1, y1), (x2, y2), (x3, y3) and prints a right triangle using these coordinates on a grid. Right now I have:

 ``12345678910111213141516`` ``````int x1, y1, x2, y2, x3, y3; cout << "Please enter the triangle's coordinates: "; cin >> x1 >> y1 >> x2 >> y2 >> x3 >> y3; base = x2 - x1; height = y3 - y2; for(int i = height; i >= 1; ++i) { for(int j = base; j >= 1; ++j) { cout << j << " "; } cout << "\n"; }``````

This results in a bombardment of increasing numbers when I run the program. Can someone help point me in the right direction? I know how to print out a basic triangle using `for` loops but I am struggling with getting this to work with user defined coordinates.
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closed account (48T7M4Gy)
Why not show us the whole program if it's not too long? And some sample output.

line 1: doesn't make any sense if you are declaring the variable
lines 6 and 7: base and height aren't declared
Oh wow, I can't believe I typed line 1 like that. That's not how it is in my actual program. I fixed it. Here's my program:

 ``123456789101112131415161718192021222324`` ``````#include using namespace std; int main(){ int x1, y1, x2, y2, x3, y3; cout << "Please enter the triangle's coordinates: "; cin >> x1 >> y1 >> x2 >> y2 >> x3 >> y3; int base = x2 - x1; int height = y2 - y1; for(int i = height; i >= 1; ++i) { for(int j = base; j >= 1; ++j) { cout << j << " "; } cout << "\n"; } return 0; }``````

My logic is, I'm sure, way off. I hope there's enough here to work with.
What I really need help with is the for loops. I can fix my math for finding base and height, but once I do, I need a better understanding of how to work with those variables in the for loops to print out a triangle properly.
closed account (48T7M4Gy)
OK that's better. So to save us a lot of time what's say you hard code the values for the coordinates and edit that post. Just comment out the cin on line 10 - don't delete it and add a couple of lines x1 = whatever etc
Here's the updated code with hardcoded variables:

 ``1234567891011121314151617181920212223242526272829`` ``````#include using namespace std; int main(){ int x1 = 0, y1 = 0, x2 = 4, y2 = 0, x3 = 4, y3 = 4; //cout << "Please enter the triangle's coordinates: "; // cin >> x1 >> y1 >> x2 >> y2 >> x3 >> y3; int base = x2 - x1; int height = y2 - y1; for(int i = height; i >= 1; ++i) { for(int j = base; j >= 1; ++j) { cout << j << " "; } cout << "\n"; } return 0; }``````
Last edited on
closed account (48T7M4Gy)
Good
closed account (48T7M4Gy)
I'm still trying to work out what you're supposed to be doing but here's a start. Look carefully at what of changed. > vs < , the values of base and height are suss too so print them out is a good move or use a debugger.

Printing blank spaces is a bad move because you don't get feedback while you're testing.

It's starting to make sense though.

 ``1234567891011121314151617181920212223242526272829`` ``````#include using namespace std; int main(){ int x1 = 0, y1 = 0, x2 = 4, y2 = 0, x3 = 4, y3 = 4; //cout << "Please enter the triangle's coordinates: "; // cin >> x1 >> y1 >> x2 >> y2 >> x3 >> y3; int base = x2 - x1; int height = y2 - y1; for(int i = 0; i < 5; ++i) { for(int j = 0; j < 5; ++j) { cout << i << "*"; } cout << "\n"; } return 0; }``````
closed account (48T7M4Gy)
So far, height = 0 !!
int height = y3 - y2; !!
closed account (48T7M4Gy)
 ``12345678910111213141516171819202122232425262728293031`` ``````#include using namespace std; int main(){ int x1 = 0, y1 = 0, x2 = 4, y2 = 0, x3 = 3, y3 = 4; //cout << "Please enter the triangle's coordinates: "; // cin >> x1 >> y1 >> x2 >> y2 >> x3 >> y3; int base = x2 - x1; int height = y3 - y2; cout << "base " << base << " height " << height << '\n'; for(int i = 0; i < base; ++i) { for(int j = i; j < height; ++j) { cout << i << "*"; } cout << "\n"; } return 0; }``````

 base 4 height 4 0*0*0*0* 1*1*1* 2*2* 3* Program ended with exit code: 0

This probably gives you enough to play arround with. :)
Thank you so much for your help! This has given me a great start. I will play around with the code :)
closed account (48T7M4Gy)
y1 and x3 aren't used - they would be used if the base and height aren't aligned with the x,y axes. In which case the nested loop would need to be substantially modified - best check that you are/are not required to program for that.
 user-given coordinates (x1, y1), (x2, y2), (x3, y3) and prints a right triangle using these coordinates on a grid.

I'm a user. I give coordinates: 42 42 42 42 42 42
I'm disappointed, I did expect to see a triangle on the quintillion * quintillion grid.

In other words, what do we know about the grid? Barely large enough to fit the triangle?
(For my input, a 42*42 would be enough.)

Where is the (0,0)? Top left, bottom left, center? Is (0,1) above or below (0,0)?

I enter three points. What if I change the order of the points? Should the image change?