Problem Statement: Given an integer N, print the following pattern :
Here, N = 5.
Examples:
Input Format: N = 3 Result: ****** ** ** * * * * ** ** ****** Input Format: N = 6 Result: ************ ***** ***** **** **** *** *** ** ** * * * * ** ** *** *** **** **** ***** ***** ************
Solution
Disclaimer: Don’t jump directly to the solution, try it out yourself first.
Approach:
There are 4 general rules for solving a pattern-based question :
- We always use nested loops for printing the patterns. For the outer loop, we count the number of lines/rows and loop for them.
- Next, for the inner loop, we focus on the number of columns and somehow connect them to the rows by forming a logic such that for each row we get the required number of columns to be printed.
- We print the numbers inside the inner loop.
- Observe symmetry in the pattern or check if a pattern is a combination of two or more similar patterns.
Contrary to the previous patterns, this pattern observes symmetry. We can clearly see that the first half of the pattern is just a mirror image of the second half of the pattern. If we observe the first part, we see that like some previous patterns, it can also be divided into 3 parts i.e. stars, spaces, and then stars. In the first row, there are no spaces and 10 stars, in the second row, there are 2 spaces and 8 stars, and so on. So, we initialize the spaces with 0 initially which will eventually increment by 2 whenever we enter a new row. The stars, however, will be twice the row number, half of the stars would be printed before the spaces and half after the spaces.
Similar will be the case of the second half of the pattern too. The initial number of spaces would be equal to 2*(N-1) and 1 star each would be printed on either side of the spaces initially. The spaces will decrease by 2 and the stars will increase by 2 in each row.
Code:
C++ Code
#include <bits/stdc++.h>
using namespace std;
void pattern19(int N)
{
// for the upper half of the pattern.
// initial spaces.
int iniS = 0;
for(int i=0;i< N;i++){
//for printing the stars in the row.
for(int j=1;j<=N-i;j++){
cout<<"*";
}
//for printing the spaces in the row.
for(int j=0;j<iniS;j++){
cout<<" ";
}
//for printing the stars in the row.
for(int j=1;j<=N-i;j++){
cout<<"*";
}
// The spaces increase by 2 every time we hit a new row.
iniS+=2;
// As soon as the stars for each iteration are printed, we move to the
// next row and give a line break otherwise all stars
// would get printed in 1 line.
cout<<endl;
}
// for lower half of the pattern
// initial spaces.
iniS = 2*N -2;
for(int i=1;i<=N;i++){
//for printing the stars in the row.
for(int j=1;j<=i;j++){
cout<<"*";
}
//for printing the spaces in the row.
for(int j=0;j<iniS;j++){
cout<<" ";
}
//for printing the stars in the row.
for(int j=1;j<=i;j++){
cout<<"*";
}
// The spaces decrease by 2 every time we hit a new row.
iniS-=2;
// As soon as the stars for each iteration are printed, we move to the
// next row and give a line break otherwise all stars
// would get printed in 1 line.
cout<<endl;
}
}
int main()
{
// Here, we have taken the value of N as 5.
// We can also take input from the user.
int N = 5;
pattern19(N);
return 0;
}
Output
**********
**** ****
*** ***
** **
* *
* *
** **
*** ***
**** ****
**********
Java Code
class Main {
static void pattern19(int N)
{
// for the upper half of the pattern.
// initial spaces.
int iniS = 0;
for(int i=0;i< N;i++){
//for printing the stars in the row.
for(int j=1;j<=N-i;j++){
System.out.print("*");
}
//for printing the spaces in the row.
for(int j=0;j<iniS;j++){
System.out.print(" ");
}
//for printing the stars in the row.
for(int j=1;j<=N-i;j++){
System.out.print("*");
}
// The spaces increase by 2 every time we hit a new row.
iniS+=2;
// As soon as the letters for each iteration are printed, we move to the
// next row and give a line break otherwise all letters
// would get printed in 1 line.
System.out.println();
}
// for lower half of the pattern
// initial spaces.
iniS = 2*N -2;
for(int i=1;i<=N;i++){
//for printing the stars in the row.
for(int j=1;j<=i;j++){
System.out.print("*");
}
//for printing the spaces in the row.
for(int j=0;j<iniS;j++){
System.out.print(" ");
}
//for printing the stars in the row.
for(int j=1;j<=i;j++){
System.out.print("*");
}
// The spaces decrease by 2 every time we hit a new row.
iniS-=2;
// As soon as the letters for each iteration are printed, we move to the
// next row and give a line break otherwise all letters
// would get printed in 1 line.
System.out.println();
}
}
public static void main(String[] args) {
// Here, we have taken the value of N as 5.
// We can also take input from the user.
int N = 5;
pattern19(N);
}
}
Output
**********
**** ****
*** ***
** **
* *
* *
** **
*** ***
**** ****
**********
Special thanks to Priyanshi Goel for contributing to this article on takeUforward. If you also wish to share your knowledge with the takeUforward fam, please check out this article. If you want to suggest any improvement/correction in this article please mail us at [email protected]