# Pascal Triangle program in C

I've created a program to calculate Pascal's triangle:

#include <stdio.h>
#include <stdlib.h>
void pascal(int limit)
{
int *begin;
begin=(int*)malloc(2*sizeof(int));
*begin=1;
*(begin+1)=1;
int* p,q,s,t;
int row=2,n=3,x;
p=begin;
q=begin+1;
for(n=3;n<=limit+1;n++)
{
if(n==4)
{
free(begin);
}
x=1;
printf("Row (%d) : ",row);
for(int* i=p;i&lt;=q;i=i+1)
{
printf("%d ",*i);
}
putchar('\n');
s=(int*)malloc(n*sizeof(int));
t=s+n-1;
*s=*p;
*t=*q;
for(int* g=p;g&lt;q;g=g+1)
{
*(s+x)=*g+*(g+1);
x++;
}
p=s;
q=t;
row++;
}
}

int main(void)
{
int i;
printf("Till which row would you like to calculate the Pascal Triangle?\n\n");
printf("Type your answer:\t");
scanf("%d",&i);
putchar('\n');
if(i<n)
printf("Nope, you can't do that\n");
else
{
printf("Row (1) : 1\n");
pascal(i);
}
}


My idea was to work with 2 arrays at the same time, but there is still a problem in my algorithm. How am I supposed to free the memory I allocated before? The first 8 bytes of begin are easy to free, but what should I do so I can free the memory I allocated through the pointers?

• Please format your code! – MrSmith42 Mar 14 '14 at 10:04
• Can someone please explain to me what does "format your code" mean? Thank you. – Giorgos Patelis Mar 14 '14 at 10:09
• Indent blocks, remove empty lines (if they are not needed for better reading) ... You can e.g use prettyprinter.de/module.php?name=PrettyPrinter – MrSmith42 Mar 14 '14 at 10:10
• Thank you so much.This is webseit is really useful.By the way is it good this way? – Giorgos Patelis Mar 14 '14 at 10:25
• How to format a code is a matter of taste, every developer likes it a bit different. But the main reason is, that the code is easier to read when the code is formatted. – MrSmith42 Mar 14 '14 at 10:48

## 1 Answer

• you don't free s which means you have a memory leak

• *(begin+1) can be rewritten as begin[1], which is much clearer

• 1 char variable names are very hard to get into, use longer/descriptive names where needed

the entire function can be rewritten as

void pascal(int limit)
{

int *row;
row=(int*)malloc(2*sizeof(int));
row[0]=1;
row[1]=1;

for(int n=3;n<=limit+1;n++){

printRow(buffer,n);

int* nextRow = (int*)malloc((1+n)*sizeof(int));
nextRow[0]=row[0];
nextRow[n]=row[n-1];

for(int i=1;i<n;i++){
nextRow[i]=row[i-1]+row[i];
}
free(row);
row=nextRow;

}
}


instead of the malloc->assign->free sequence I could have used realloc and then worked backwards:

row = (int*)realloc(row,(1+n)*sizeof(int));
row[n]=0;

for(int i=n;i>0;i--){
row[i]+=row[i-1];
}


but this is less clear