Change/add only one character and print '*' exactly 20 times

In the below code, change/add only one character and print ‘*’ exactly 20 times.

int main()
{
    int i, n = 20;
    for (i = 0; i < n; i--)
        printf("*");             
    getchar();
    return 0;
}

Solutions:

1. Replace i by n in for loop’s third expression

C++

#include <iostream> 
using namespace std; 
int main() 
{ 
    int i, n = 20; 
    for (i = 0; i < n; n--) 
        cout << "*"; 
    getchar();  
    return 0; 
} 

C

#include <stdio.h> 
int main() 
{ 
    int i, n = 20; 
    for (i = 0; i < n; n--) 
        printf("*"); 
    getchar();     
    return 0; 
} 

Java

// Java code 
class GfG {  
public static void main(String[] args)  
{  
    int i, n = 20;  
    for (i = 0; i < n; n--)  
        System.out.print("*");  
}  
}  

C#

// C# code 
using System; 
class GfG  
{  
    public static void Main()  
    {  
        int i, n = 20;  
        for (i = 0; i < n; n--)  
            Console.Write("*");  
    }  
}  
  
// This code is contributed by SoumikMondal 

2. Put ‘-‘ before i in for loop’s second expression

#include <stdio.h> 
int main() 
{ 
    int i, n = 20; 
    for (i = 0; -i < n; i--) 
        printf("*");            
    getchar();     
    return 0; 
} 

3. Replace < by + in for loop's second expression

#include <stdio.h> 
int main() 
{ 
    int i, n = 20; 
    for (i = 0; i + n; i--) 
       printf("*"); 
    getchar(); 
    return 0; 
} 

Let’s extend the problem little.

Change/add only one character and print ‘*’ exactly 21 times.

Solution: Put negation operator before i in for loop’s second expression.

Explanation: Negation operator converts the number into its one’s complement.

       No.              One's complement
 0 (00000..00)            -1 (1111..11)                         
-1 (11..1111)             0 (00..0000)                        
-2 (11..1110)             1 (00..0001)                            
-3 (11..1101)             2 (00..0010)
...............................................
-20 (11..01100)           19 (00..10011)

#include <stdio.h> 
int main() 
{ 
    int i, n = 20; 
    for (i = 0; ~i < n; i--)  
        printf("*"); 
    getchar(); 
    return 0; 
} 

Please comment if you find more solutions of above problems.

My Personal Notes

Change/add only one character and print ‘*’ exactly 20 times

C++

C

Java

C#

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