Program to print the Zigzag pattern

Given a number N denoting the number of rows. The task is to print the zigzag pattern with N rows as shown in the below examples.
Examples: 

Input : N = 3 
Output : 1 
         3*2 
         4*5*6

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

Approach: 

1. Use a for loop for printing the number of rows.
2. Use two variables var and var1 for odd and even rows respectively.
3. When the row number is odd, calculate starting point of the row and then print and increment the variable simultaneously.
4. When the row number is even, calculate corresponding starting point and print and decrement the variable simultaneously.

Below is the implementation of the above approach: 

C++

// CPP program to print the given
// zigzag pattern

#include<iostream>
using namespace std;

// Function to print the zigzag pattern
void printPattern(int n)
{
    int var1, var = 1;

    for(int i = 1; i <= n; i++)
    {
        // for odd rows
        if(i%2!=0)
        {
            // calculate starting value
            var = var + i - 1;
            for(int j=1; j<=i; j++)
            {
                if(j==1)
                {
                    cout<<var;
                }
                else
                   cout<<"*"<<var;

               var++;
            }
        }
        else // for even rows
        {
            var1 = var + i -1; // calculate starting value
            for(int j=1; j<=i; j++)
            {
                if(j==1)
                {
                    // print without star
                    cout<<var1;
                }
                else
                {
                    // print with star
                    cout<<"*"<<var1;
                }
                var1--;
            }
        }
        cout<<endl;
    }

}

// Driver code
int main()
{
    int n = 5;

    printPattern(n);

    return 0;
}

Java

// Java program to print the given
// zigzag pattern
class GFG
{
// Function to print the
// zigzag pattern
static void printPattern(int n)
{
    int var1, var = 1;

    for(int i = 1; i <= n; i++)
    {
        // for odd rows
        if(i % 2 != 0)
        {
            // calculate starting value
            var = var + i - 1;
            for(int j = 1; j <= i; j++)
            {
                if(j == 1)
                {
                    System.out.print(var);
                }
                else
                System.out.print("*" + var);

            var++;
            }
        }
        else // for even rows
        {
            var1 = var + i -1; // calculate starting value
            for(int j = 1; j <= i; j++)
            {
                if(j == 1)
                {
                    // print without star
                    System.out.print(var1);
                }
                else
                {
                    // print with star
                    System.out.print("*" + var1);
                }
                var1--;
            }
        }
        System.out.print("\n");
    }

}

// Driver code
public static void main(String [] arg)
{
    int n = 5;

    printPattern(n);
}
}

// This code is contributed by Smitha

Python3

# Python3 program to print the given
# zigzag pattern

# Function to print the zigzag pattern
def printPattern(n):

    var = 0
    var = 1

    for i in range(1, n + 1):

        # for odd rows
        if(i % 2 != 0):

            # calculate starting value
            var = var + i - 1
            for j in range(1, i + 1):

                if(j == 1):

                    print(var, end = "")
                else:
                    print("*", end = "")
                    print(var, end = "")

                var += 1


        else: # for even rows

            var1 = var + i -1 # calculate starting value
            for j in range(1, i + 1):

                if(j == 1):

                    # prwithout star
                    print(var1, end = "")

                else:

                    # prwith star
                    print("*", end = "")
                    print(var1, end = "")

                var1 -= 1

        print()

# Driver code
n = 5

printPattern(n)

# This code is contributed by Mohit kumar

C#

// C# program to print the given
// zigzag pattern
using System;
class GFG
{
// Function to print the
// zigzag pattern
static void printPattern(int n)
{
    int var1, var = 1;

    for(int i = 1; i <= n; i++)
    {
        // for odd rows
        if(i % 2 != 0)
        {
            // calculate starting value
            var = var + i - 1;
            for(int j = 1; j <= i; j++)
            {
                if(j == 1)
                {
                    Console.Write(var);
                }
                else
                    Console.Write("*" + var);

            var++;
            }
        }
        else // for even rows
        {
            var1 = var + i -1; // calculate starting value
            for(int j = 1; j <= i; j++)
            {
                if(j == 1)
                {
                    // print without star
                    Console.Write(var1);
                }
                else
                {
                    // print with star
                    Console.Write("*" + var1);
                }
                var1--;
            }
        }
        Console.Write("\n");
    }

}

// Driver code
public static void Main()
{
    int n = 5;

    printPattern(n);
}
}

// This code is contributed
// by Akanksha Rai(Abby_akku)

PHP

<?php
// PHP program to print the given
// zigzag pattern

// Function to print the zigzag pattern
function printPattern($n)
{
    $var1; $var = 1;

    for($i = 1; $i <= $n; $i++)
    {
        // for odd rows
        if($i % 2 != 0)
        {
            // calculate starting value
            $var = $var + $i - 1;
            for($j = 1; $j <= $i; $j++)
            {
                if($j == 1)
                {
                    echo $var;
                }
                else
                    echo "*" . $var;

                $var++;
            }
        }
        else // for even rows
        {
            // calculate starting value
            $var1 = $var + $i - 1;
            for($j = 1; $j <= $i; $j++)
            {
                if($j == 1)
                {
                    // print without star
                    echo $var1;
                }
                else
                {
                    // print with star
                    echo "*" . $var1;
                }
                $var1--;
            }
        }
        echo "\n";
    }

}

// Driver code
$n = 5;

printPattern($n);

// This code is contributed by Rajput-Ji
?>

Javascript

<script>
      // JavaScript program to print the given
      // zigzag pattern

      // Function to print the zigzag pattern
      function printPattern(n)
      {
        var var1,
          var2 = 1;

        for (var i = 1; i <= n; i++)
        {

          // for odd rows
          if (i % 2 != 0)
          {

            // calculate starting value
            var2 = var2 + i - 1;
            for (var j = 1; j <= i; j++)
            {
              if (j == 1)
              {
                document.write(var2);
              }
              else document.write("*" + var2);

              var2++;
            }
          }

          // for even rows
          else
          {
            var1 = var2 + i - 1; // calculate starting value
            for (var j = 1; j <= i; j++) {
              if (j == 1)
              {

                // print without star
                document.write(var1);
              }
              else
              {

                // print with star
                document.write("*" + var1);
              }
              var1--;
            }
          }
          document.write("<br>");
        }
      }

      // Driver code
      var n = 5;
      printPattern(n);

      // This code is contributed by rdtank.
    </script>

Output:

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

Time Complexity: O(N^2)
Auxiliary Space: O(1)