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Print the following pyramid pattern
  • Difficulty Level : Medium
  • Last Updated : 29 Apr, 2021

Given a positive integer n. The problem is to print the pyramid pattern as described in the examples below.

Examples: 

Input : n = 4
Output : 
1
3*2
4*5*6
10*9*8*7

Input : n = 5
Output :
1
3*2
4*5*6
10*9*8*7
11*12*13*14*15

Source: Amdocs Interview Experience | Set 1
 

Approach: For odd number row, values are being displayed in increasing order and for even number row, values are being displayed in decreasing order. The only other trick is to how to iterate the loops.

Algorithm: 

printPattern(int n)
    Declare j, k
    Initialize k = 0

    for i = 1 to n

    if i%2 != 0
        for j = k+1, j < k+i, j++
        print j and "*"
        print j and new line    
        k = ++j

    else
        k = k+i-1
        for j = k, j > k-i+1, j--
        print j and "*";
        print j and new line

C++




// C++ implementation to print the following
// pyramid pattern
#include <bits/stdc++.h>
using namespace std;
 
// function to print the following pyramid pattern
void printPattern(int n)
{
    int j, k = 0;
     
    // loop to decide the row number
    for (int i=1; i<=n; i++)
    {
        // if row number is odd
        if (i%2 != 0)
        {
            // print numbers with the '*' sign in
            // increasing order
            for (j=k+1; j<k+i; j++)
                cout << j << "*";
            cout << j++ << endl;
             
            // update value of 'k'    
            k = j;    
        }
         
        // if row number is even
        else
        {
            // update value of 'k'
            k = k+i-1;
             
            // print numbers with the '*' in
            // decreasing order
            for (j=k; j>k-i+1; j--)
                cout << j << "*";
            cout << j << endl;    
        }
    }
}
 
// Driver program to test above
int main()
{
    int n = 5;
    printPattern(n);
    return 0;
}

Java




// Java implementation to print the
// following pyramid pattern
public class Pyramid_Pattern {
 
    // function to print the following pyramid
    // pattern
    static void printPattern(int n)
    {
        int j, k = 0;
 
        // loop to decide the row number
        for (int i = 1; i <= n; i++) {
             
            // if row number is odd
            if (i % 2 != 0) {
             
                // print numbers with the '*'
                // sign in increasing order
                for (j = k + 1; j < k + i; j++)
                    System.out.print(j + "*");
                System.out.println(j++);
 
                // update value of 'k'
                k = j;
            }
 
            // if row number is even
            else {
                 
                // update value of 'k'
                k = k + i - 1;
 
                // print numbers with the '*' in
                // decreasing order
                for (j = k; j > k - i + 1; j--)
                    System.out.print(j + "*");
                System.out.println(j);
            }
        }
    }
 
    // Driver program to test above
public static void main(String args[])
    {
        int n = 5;
        printPattern(n);
    }
}
// This code is contributed by Sumit Ghosh

Python3




# Python3 implementation to print the
# following pyramid pattern
 
# function to print the
# following pyramid pattern
def printPattern(n) :
 
    j, k = 0, 0
 
    # loop to decide the row number
    for i in range(1, n + 1) :
 
        # if row number is odd
        if i % 2 != 0 :
 
            # print numbers with
            # the '*' sign in
            # increasing order
            for j in range(k + 1, k + i) :
 
                print(str(j) + "*",
                        end = "")
 
            j = k + i
            print(j)
            j += 1
 
            # update value of 'k'
            k = j
 
        # if row number is even
        else :
 
            # update value of 'k'
            k = k + i - 1
 
            # print numbers with the
            # '*' in decreasing order
            for j in range(k, k - i + 1, -1) :
                print(str(j) + "*", end = "")
 
            j = k - i + 1
            print(j)
 
# Driver Code
if __name__ == "__main__" :
    n = 5
 
    # function calling
    printPattern(n)
             
# This code is contributed
# by ANKITRAI1

C#




// C# implementation to print the
// following pyramid pattern
using System;
public class Pyramid_Pattern {
 
    // function to print the following pyramid
    // pattern
    static void printPattern(int n)
    {
        int j, k = 0;
 
        // loop to decide the row number
        for (int i = 1; i <= n; i++) {
             
            // if row number is odd
            if (i % 2 != 0) {
             
                // print numbers with the '*'
                // sign in increasing order
                for (j = k + 1; j < k + i; j++)
                    Console.Write(j + "*");
                Console.WriteLine(j++);
 
                // update value of 'k'
                k = j;
            }
 
            // if row number is even
            else {
                 
                // update value of 'k'
                k = k + i - 1;
 
                // print numbers with the '*' in
                // decreasing order
                for (j = k; j > k - i + 1; j--)
                    Console.Write(j + "*");
                    Console.WriteLine(j);
            }
        }
    }
 
    // Driver program to test above
public static void Main()
    {
        int n = 5;
        printPattern(n);
    }
}
// This code is contributed by vt_m.

PHP




<?php
// PHP implementation to print the
// following pyramid pattern
 
// function to print the following
// pyramid pattern
function printPattern($n)
{
    $k = 0;
     
    // loop to decide
    // the row number
    for ($i = 1; $i <= $n; $i++)
    {
         
        // if row number is odd
        if ($i % 2 != 0)
        {
             
            // print numbers with the '*'
            // sign in increasing order
            for ($j = $k + 1; $j < $k + $i; $j++)
                echo $j. "*";
            echo $j++ ."\n";
             
            // update value of 'k'
            $k = $j;
        }
         
        // if row number is even
        else
        {
             
            // update value of 'k'
            $k = $k + $i - 1;
             
            // print numbers with the
            // '*' in decreasing order
            for ($j = $k; $j > $k - $i + 1; $j--)
                echo $j . "*";
            echo $j ."\n" ;
        }
    }
}
 
    // Driver Code
    $n = 5;
    printPattern($n);
 
// This code is contributed by Sam007
?>

Javascript




<script>
 
// JavaScript implementation to print the
// following pyramid pattern
 
// Function to print the following
// pyramid pattern
function printPattern(n)
{
    var j, k = 0;
     
    // Loop to decide the row number
    for(var i = 1; i <= n; i++)
    {
         
        // If row number is odd
        if (i % 2 != 0)
        {
             
            // Print numbers with the '*'
            // sign in increasing order
            for(j = k + 1; j < k + i; j++)
                document.write(j + "* ");
                 
            document.write(j++ + "<br>");
 
            // Update value of 'k'
            k = j;
        }
 
        // If row number is even
        else
        {
             
            // Update value of 'k'
            k = k + i - 1;
 
            // Print numbers with the '*' in
            // decreasing order
            for(j = k; j > k - i + 1; j--)
                document.write(j + "*");
                 
            document.write(j + "<br>");
        }
    }
}
 
// Driver code
var n = 5;
 
printPattern(n);
 
// This code is contributed by akshitsaxenaa09
 
</script>

Output: 

1
3*2
4*5*6
10*9*8*7
11*12*13*14*15

Time Complexity: O((n * (n + 1)) / 2)
This article is contributed by Ayush Jauhari. If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.
Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above.
 




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