[c]
#include "stdafx.h"
 
#include <stdio.h>

constint leftCorner = 3;
constint rightCorner = 4;
constint topElement = 2;
int *oldTriangle = 0;
int *newTriangle = 0;
void displayTriangle (int iteration)
{
if ((iteration % 2) == 1) 
{
for (int i = 1; i <= iteration; ++i)
printf ("%d ", oldTriangle[i-1]);
}
else
{
for (int i = 1; i <= iteration; ++i)
printf ("%d ", newTriangle[i-1]);
}
printf ("\n");
}
 
int buildTriangle (int tmpPascalRow)
{
int tmpRow, elementIndex;
int* src = NULL;
int* dest = NULL;
 
 
oldTriangle[0] = topElement;
displayTriangle (1);
if (tmpPascalRow == 1)
return 1;
 
newTriangle[0] = leftCorner;
newTriangle[1] = rightCorner;
displayTriangle (2);
if (tmpPascalRow == 2)
return 1;
 
for (tmpRow = 3; tmpRow <= tmpPascalRow; ++tmpRow)
{
if ((tmpRow % 2) == 1)
{
dest = oldTriangle;
src = newTriangle;
}
else
{
dest = newTriangle;
src = oldTriangle;
}
 
dest[0] = src[0];
dest[tmpRow-1] = src[tmpRow-2];
for (elementIndex = 1; elementIndex < tmpRow - 1; ++elementIndex)
{
dest[elementIndex] = src[elementIndex] + src[elementIndex - 1];
}
displayTriangle (tmpRow);
}
}
 
int main (void)
{
char inputBuffer[10];
int pascalRow = 0;
int index;
 
fputs ("Enter the number of rows required: ", stdout);
fgets (inputBuffer, sizeof (inputBuffer), stdin);
fflush (stdin);
pascalRow = atoi (inputBuffer);
newTriangle = (int*) calloc (pascalRow, sizeof (int));
oldTriangle = (int*) calloc (pascalRow, sizeof (int));
buildTriangle (pascalRow);
getchar();
return 0;
}
[/c]

declare variable, lines, to hold number of lines in the pascals triangle
prompt user to enter number of lines
store number of lines from user in lines

declare pascals triangle to be a pointer to pointer to type int like this:
int ** pascalsTri;

//allocate memory for an array of pointer to int
pascalsTri = new int *[lines];

//for each pointer to int allocate memory for an array of int
for(int i = 0; i < lines; ++i)
  pascalsTri[i] = new int[lines];

declare two ints, row and col, to act as indices to access ints in pascalsTri

pascalsTri is now equivalent to:

int pascalsTri[lines][lines];

and any given int in pascalsTri can be refered to individually using pascalsTri[row][col] with the appropriate values of row and col.

declare variables to hold the three given values of the triangle; topCorner, rightCorner, leftCorner.

prompt user for value of each variable and store it appropriately

now use rightCorner, leftCorner, row and col to get the other values of the triangle

for each row starting with row 2 up to and including the value lines - 1
  for each col starting with 0 up to and including the value of row 
     if(col == 0)
       pascalTri[row][col] = leftCorner;
     else if(col == row)
       pascalTri[row][col] = rightCorner;
     else
       assign the sum of the int at pascalTri[row - 1][col - 1] plus pascalTri[row -1][col] to the current int with indices row and col