Write a C program to print pascal triangle up to n rows using loop. Logic to print Pascal triangle in C programming. How to print Pascal triangle of n rows using loop in C program.

**Example**

**Input**

Input rows: 5

**Output**

1 1 1 1 2 1 1 3 3 1 1 4 6 4 1

## Required knowledge

Basic C programming, For loop, While loop, Nested loop, Functions

### Pascal Triangle

Pascal triangle is a triangular number pattern named after famous mathematician Blaise Pascal.

For example Pascal triangle with 6 rows.

## Logic to print pascal triangle

To find n^{th} term of a pascal triangle we use following formula.

Where `n` is row number and `k` is term of that row.

Step by step descriptive logic to print pascal triangle.

- Input number of rows to print from user. Store it in a variable say
`num`. - To iterate through rows, run a loop from 0 to
`num`, increment 1 in each iteration. The loop structure should look like`for(n=0; n<num; n++)`

. - Inside the outer loop run another loop to print terms of a row. Initialize the loop from 0 that goes to
`n`, increment 1 in each iteration. - Inside the inner loop use formula
`term = fact(n) / (fact(k) * fact(n-k));`

to print current term of pascal triangle.Here,

`fact()`

is a function defined to find factorial of a number.

## Program to print Pascal triangle

```
/**
* C program to print Pascal triangle up to n rows
*/
#include <stdio.h>
/* Function definition */
long long fact(int n);
int main()
{
int n, k, num, i;
long long term;
/* Input number of rows */
printf("Enter number of rows : ");
scanf("%d", &num);
for(n=0; n<num; n++)
{
/* Prints 3 spaces */
for(i=n; i<=num; i++)
printf("%3c", ' ');
/* Generate term for current row */
for(k=0; k<=n; k++)
{
term = fact(n) / (fact(k) * fact(n-k));
printf("%6lld", term);
}
printf("\n");
}
return 0;
}
/**
* Function to calculate factorial
*/
long long fact(int n)
{
long long factorial = 1ll;
while(n>=1)
{
factorial *= n;
n--;
}
return factorial;
}
```

Let us take a note of the above program.

- The statement
`printf("%3c", ' ');`

is used to print 3 white spaces and is equivalent to`printf(" ");`

. - The statement
`printf("%6lld", term);`

prints the current term with 6 character width. - To print a
`long long`

type value I have used`%lld`

format specifier. - In the
`fact()`

function I have added`ll`

suffix while declaring`long long factorial = 1ll;`

. Since 1 is an integer variable, hence to tell the compiler explicitly that store 1 as`long long`

type I have added the suffix.Read more - Literals in C programming.

Output

Enter number of rows : 10 1 1 1 1 2 1 1 3 3 1 1 4 6 4 1 1 5 10 10 5 1 1 6 15 20 15 6 1 1 7 21 35 35 21 7 1 1 8 28 56 70 56 28 8 1 1 9 36 84 126 126 84 36 9 1

Happy coding 😉

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