Help printing a triangle

[scoutlikescookies]

Hi there. Hoping someone can explain what I am doing wrong.
This is supposed to out a triangle shape, but I am just getting a straight line.

  #include <iostream>
#include <iomanip>

using namespace std;

int length;
int i,j,k;
char symbol=1;

int main ( ) 
{
    cout << "Enter a value to represent the base of a triangle shape (not to exceed 80): ";
    cin >> length;
    length = length + 1;
    cout << "\n";
    
    cout << "Enter the character to be used to generate the filled-in triangle shape (for eg., #, * $): ";
    cin >> symbol;
    cout << "\n";
    
    for(i = length; i <= length; i++) 
    {
        for (j = length; j > i; j--)
			cout<<' ';
			
	    for (k = length; k < 2*i; k++)
			cout<<'*';
		
		cout << endl;
    }
    
}

OUTPUT:
Enter a value to represent the base of a triangle shape (not to exceed 80): 11

Enter the character to be used to generate the filled-in triangle shape (for eg., #, * $): *

************

[Naughty Albatross]

Hi,

for(i = length; i <= length; i++) 
    {
        for (j = length; j > i; j--)
			cout<<' ';
			
	    for (k = length; k < 2*i; k++)
			cout<<'*';
		
		cout << endl;
    }

==>

for (int i = length; i >= 1; i--)
{
    for (int j = i; j >= 1; j--) cout << symbol;
    cout << endl;
}

[Naughty Albatross]

Also :

cin >> length;
length = length + 1;
cout << "\n";

[Naughty Albatross]

> This is supposed to out a triangle shape, but I am just getting a straight line.
for(i = length; i <= length; i++) {}

Now (i = length).
When your program finishes the first loop, (i) is increased by 1 (now (i > length)). When your program enters the next loop, it will check the condition (i <= length) which is always false, hence breaking the loop.

[Naughty Albatross]

Does that help you? :)

[scoutlikescookies]

Hi there, thanks so much for your help. That makes sense, but now I am getting an infinite output of *'s, instead of just a line. How can I make this become a triangle instead?

[Naughty Albatross]

> How can I make this become a triangle instead?
Try this again. It is still the same thing as before, but this one will do what you want :)

for (int i = length; i >= 1; i--)
{
    for (int j = i; j >= 1; j--) cout << symbol;
    cout << endl;
}

[Naughty Albatross]

Does that? : )

[48T7M4Gy]

  #include <iostream>
#include <iomanip>

using namespace std;

int length;
int i,j,k;
char symbol=1;

int main ( ) 
{
    cout << "Enter a value to represent the base of a triangle shape (not to exceed 80): ";
    cin >> length;
    length = length + 1;
    cout << "\n";
    
    cout << "Enter the character to be used to generate the filled-in triangle shape (for eg., #, * $): ";
    cin >> symbol;
    cout << "\n";
    
    for(i = 0; i <= length; i++) // <--
    {
        for (j = length; j > i; j--)
			cout<<' ';
			
	    for (k = length; k < 2*i; k++)
			cout<< symbol; // <--
		
		cout << endl;
    }
    
}

Enter a value to represent the base of a triangle shape (not to exceed 80): 10

Enter the character to be used to generate the filled-in triangle shape (for eg., #, * $): f

           
          
         
        
       
      
     *
    ***
   *****
  *******
 *********
***********

[48T7M4Gy]

#include <iostream>

int main ( )
{
    int length = 0;
    char symbol = '*';
    bool keep_going = true;
    
    do{
        std::cout << "Enter base size of triangle (1 - 80 inclusive): ";
        std::cin >> length;
        
        if ( length < 1 || length > 80)
            keep_going = true;
        else
        {
            std::cout << "Enter symbol to display triangle (eg., #, * $): ";
            std::cin >> symbol;
            
            keep_going = false;
        }
    }while (keep_going == true);
    
    for( int i = 0; i <= length; i++)
    {
        for(int j = 0; j < length - i ; j++)
            std::cout << ' ';
        
        for(int k = 0; k < 2 * i - 1; k++)
            std::cout << symbol;
        std::cout << '\n';
    }
    return 0;
}

[48bpfSEw]

With animation:

/**
 DRAW TRIANGLE
 2016 by Necip
**/

#include <windows.h>
#include <iostream>
#include <conio.h>
#include <time.h>

/*********************
 SYSTEM HELP FUNCTIONS
 *********************/  

/**
 Sleep process to slow down application
 **/
void sleepcp(int milliseconds) {
    clock_t time_end;
    time_end = clock() + milliseconds * CLOCKS_PER_SEC/1000;
    while (clock() < time_end) { }
}
  
/**
 Get Key Stroke
 **/  
char getkey (void) {
  if (kbhit()) {
    char c = getch();
    if (c != '\0')
      return c;
    }  
  sleepcp(100);
  return 0;
  }
  
/**
 Goto position x,y on display
 **/  
void gotoPos (int x, int y) {
  COORD c = {x,y};
  SetConsoleCursorPosition(GetStdHandle(STD_OUTPUT_HANDLE),c);
}

/**
 Print string on x,y at display
 **/  

void printPos (int x, int y, char* pszBuffer) {
  gotoPos (x,y);
  std::cout << pszBuffer;
  }

/**
 Print char on x,y at display
 **/    
void printPos (int x, int y, char c) {
  gotoPos (x,y);
  std::cout << c;
  }
    
      
/*********************
 GAME DEFINTIONS
 *********************/  
      
/**
 Characters of the input file
 **/       
const char CH_WALL    = 'W'; 
const char CH_GROUND  = 'G'; 
const char CH_STONE   = 'O'; 
const char CH_SPACE   = ' '; 
const char CH_EXIT    = 'X'; 
const char CH_PLAYER  = 'P'; 
const char CH_DIAMOND = '*';  

/**
 Size of play area
 **/ 
const int  MAXX         = 70;
const int  MAXY         = 20; 

/**
 Input File Content (example) 
 Area must have the size of MAXX, MAXY!
 
 W : Wall     (the frame is obligatory!)
 G : Ground
 * : Diamonds
 O : Stone
 P : Player
 X : Exit
 
 **/ 
               //  1234567890123456789012345678901234567890123456789012345678901234567890
char* ptrBuffer = "WWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWW" // 1
                  "W                                 P                                  W" // 2
                  "W                                                                    W" // 3
                  "W                                                                    W" // 4
                  "W                                                                    W" // 5
                  "W                                                                    W" // 6
                  "W                                                                    W" // 7
                  "W                                                                    W" // 8
                  "W                                                                    W" // 9
                  "W                                                                    W" // 0
                  "W                                                                    W" // 1
                  "W                                                                    W" // 2
                  "W                                                                    W" // 3
                  "W                                                                    W" // 4
                  "W                                                                    W" // 5
                  "W                                                                    W" // 6
                  "W                                                                    W" // 7
                  "W                                                                    W" // 8
                  "W                                                                    W" // 9
                  "WWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWW";// 0                                                         

/**
 Characters converted for display
 **/ 
const char CHAR_WALL    = 219; // 'W';    // ascii 219 █     
const char CHAR_SPACE   = ' ';    
const char CHAR_PLAYER  = 244; // '@';    // ascii 244 @
const char CHAR_DIAMOND = '*'; // '*';    

/**
 User Input Key Strokes
 **/ 
const char CHAR_QUIT    = 'q';      

/*********************
 GAME.H
 *********************/ 
class Game {
public:
  int  px,py;                 // x,y of player
  char cell[MAXX][MAXY];      // Game field

public:  
  Game();
 
  void load (char* pszBuffer);  // loads next level
  void show (void);             // shows game field (cells)
  void exec (int iSize);        // executes game
  
private:
  void anim (void);                               // animates next frame
  void swap (int x1, int y1, int x2, int y2);     // swaps cell contents
  };


/*********************
 GAME.CPP
 *********************/ 

/**
 **/ 
Game::Game() {
  px = -1;
  py = -1;
}
 
/**
 **/
void Game::show (void) {
  for (int y = MAXY-1; y >= 0; y--) {
    for (int x = MAXX-1; x >= 0; x--) {
      printPos (x,y, cell[x][y]); 
      }
    }
  }
    
/**
 **/
void Game::load (char* pszBuffer) {

  int x=0;
  int y=0;
  for (char* ptr = pszBuffer; *ptr; ++ptr, ++x) {
    if (x >= MAXX) {
      x = 0;
      y ++;
      }    

    switch (*ptr) {
      case CH_WALL:
        cell[x][y] = CHAR_WALL;   
        break;
      case CH_SPACE:
        cell[x][y] = CHAR_SPACE;   
        break;
      case CH_PLAYER:
        cell[x][y] = CHAR_PLAYER;   
        break;  
      }
        
    if (cell[x][y] == CHAR_PLAYER) {
      px = x;
      py = y;
      }
    }
  }
 
/**
 **/
void Game::swap(int x1, int y1, int x2, int y2) {

  char cTmp     = cell[x1][y1];
  cell[x1][y1]  = cell[x2][y2];
  cell[x2][y2]  = cTmp;

  printPos (x1,y1, cell[x1][y1]); 
  printPos (x2,y2, cell[x2][y2]);  
} 
 
/**
 **/
void Game::anim (void) {

  // User Input
  char ck = getkey ();    
  switch (ck) {
    case CHAR_QUIT:
      exit (0);
      break;
    }
  
  // Animation  
  for (int y = MAXY-2; y > 0; y--) {
    for (int x = MAXX-2; x > 0; x--) {
      char c          = cell[x  ][y  ];      
      char cDownLeft  = cell[x-1][y+1];
      char cDownRight = cell[x+1][y+1];
      char cDown      = cell[x  ][y+1];
      
      switch (c) {
        case CHAR_DIAMOND :
          if (cDown == CHAR_SPACE)
            swap (x, y, x, y+1);
          else if (cDownLeft == CHAR_SPACE)
            swap (x, y, x-1, y+1);
          else if (cDownRight == CHAR_SPACE)
            swap (x, y, x+1, y+1);
          break;
        }
      }
    }
    
    printPos (0, MAXY, "q: quit");
  }

/**
 **/
void Game::exec (int iSize) {
  for (int i=0; i < iSize; i++) {      
    cell[px][py] = CHAR_DIAMOND;
    anim ();
    }
    
  while (true) {
    anim ();
    }
  }
  
  
/*********************
 MAIN.CPP
 *********************/ 
int main (void) {

  system ("cls");
  
  printPos (0, MAXY+1, "Input size of triangle (1-10): ");
  int iSize=0;
  std::cin >> iSize;
  
  if (iSize <1 || iSize >10) {
    printPos (0, MAXY+2, "Input out of range!");
    return -1;
    }
  
  
  int iCountDiamonds = 0;
  int iDelta         = 1;
  for (int i=0;i<iSize;i++) {
    iCountDiamonds += iDelta;
    iDelta += 2;
    }
  
  Game game;
  game.load (ptrBuffer);
  game.show ();
  game.exec (iCountDiamonds);

  
  printPos (0, MAXY+1, "Finished");
   
  return 0;
}

[Naughty Albatross]

@Necip
+1