For loop pattern programs in C and C++

Practicing pattern programs is the fastest way to master for loops in C and C++. Pattern programs are a key to strengthening logic-building.

While Python may be the most accessible language to write pattern code, It is worthwhile to learn the same in C/C++ as it has less abstraction and provides better tools to practice logic building.

Simple number matrix program

#include <iostream>

int main() {
    int a;
    std::cout<<"Enter a number: ";
    std::cin>>a;
    
    //Number pyramid
    for(int i=1;i<=a;i++) {
        for(int j=1;j<=a;j++) {
            std::cout<<i<<" ";
        }
        std::cout<<"\n";
    }
}
Code language: C++ (cpp)

Output pattern

Enter a number: 5
1 1 1 1 1 
2 2 2 2 2 
3 3 3 3 3 
4 4 4 4 4 
5 5 5 5 5 
Code language: C++ (cpp)

Consecutive numbers matrix program

#include <iostream>

int main() {
    int a;
    std::cout<<"Enter a number: ";
    std::cin>>a;
    
    for(int i=1; i<=a*a; i+=a) {
        for(int j=i; j<i+a; j++) {
            std::cout<<j<<" ";
        }
        std::cout<<"\n";
    }
}
Code language: C++ (cpp)

Output pattern

Enter a number: 5
1 2 3 4 5 
6 7 8 9 10 
11 12 13 14 15 
16 17 18 19 20 
21 22 23 24 25
Code language: C++ (cpp)

Number triangle program

#include <iostream>

int main() {
    int a;
    std::cout<<"Enter a number: ";
    std::cin>>a;
    
    for(int i=1; i<=a; i++) {
        for(int j=i; j>=1; j--) {
            std::cout<<j<<" ";
        }
        std::cout<<"\n";
    }
}
Code language: C++ (cpp)

Output pattern

Enter a number: 5
1 
2 1 
3 2 1 
4 3 2 1 
5 4 3 2 1 
Code language: C++ (cpp)

Number pyramid program

#include <iostream>

int main() {
    int a;
    std::cout<<"Enter a number: ";
    std::cin>>a;
    
    for(int i=1; i<=a; i++) {
        for(int m=1; m<=a-i; m++) {
            std::cout<<"  ";
        }
        
        for(int n=i; n>=2; n--) {
            std::cout<<n<<" ";
        }
        
        for(int j=1; j<=i; j++) {
            std::cout<<j<<" ";
        }
        std::cout<<"\n";
    }
}
Code language: C++ (cpp)

Output pattern

Enter a number: 5
        1 
      2 1 2 
    3 2 1 2 3 
  4 3 2 1 2 3 4 
5 4 3 2 1 2 3 4 5 
Code language: C++ (cpp)

Alphabet matrix program

#include <iostream>

int main() {
    int a;
    std::cout<<"Enter a number: ";
    std::cin>>a;
    
    for(int i=1;i<=a;i++) {
        for(int j=(i-1)*a;j<i*a;j++) {
            char ch = 'A' + j;
            std::cout<<ch<<" ";
        }
        std::cout<<"\n";
    }
}
Code language: C++ (cpp)

Output pattern

Enter a number: 5
A B C D E 
F G H I J 
K L M N O 
P Q R S T 
U V W X Y 
Code language: C++ (cpp)

Alphabet triangle program

#include <iostream>

int main() {
    int a;
    std::cout<<"Enter a number: ";
    std::cin>>a;
    
    for(int i=a-1; i>=0; i--) {
        for(int j=i; j<a; j++) {
            char ch = 'A' + j;
            std::cout<<ch<<" ";
        }
        std::cout<<"\n";
    }
}
Code language: C++ (cpp)

Output pattern

Enter a number: 5
E 
D E 
C D E 
B C D E 
A B C D E 
Code language: C++ (cpp)

Star pyramid program

#include <iostream>

int main() {
    int a;
    std::cout<<"Enter a number: ";
    std::cin>>a;
    
    for(int i=1; i<=a; i++) {
        for(int j=1; j<=a-i; j++) {
            std::cout<<" ";
        }
        for(int k=i; k>=1; k--) {
            std::cout<<"* ";
        }
        std::cout<<"\n";
    }
}
Code language: C++ (cpp)

Output pattern

Enter a number: 5
    * 
   * * 
  * * * 
 * * * * 
* * * * * 
Code language: C++ (cpp)

Mixed pattern program

#include <iostream>

int main() {
    int a;
    std::cout<<"Enter a number: ";
    std::cin>>a;
    
    int i = 1;
    while(i<=a) {
        int j = 1;
        while(j<=a-i+1) {
            std::cout<<j<<" ";
            j++;
        }
        
        int l = (i-1)*2;
        while(l>0) {
            std::cout<<"* ";
            l--;
        }
        
        int m = a-i+1;
        while(m>=1) {
            std::cout<<m<<" ";
            m--;
        }
        
        i++;
        std::cout<<"\n";
    }
}
Code language: C++ (cpp)

Output pattern

Enter a number: 5
1 2 3 4 5 5 4 3 2 1 
1 2 3 4 * * 4 3 2 1 
1 2 3 * * * * 3 2 1 
1 2 * * * * * * 2 1 
1 * * * * * * * * 1 
Code language: C++ (cpp)

Conclusion

It is important to have concise logic building along with syntactic knowledge of a language. Now, you are all set to tackle any pattern problem that you encounter.
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