copy_paste.c

#include <stdio.h> 
  
// A recursive function that returns the optimal length string 
// for N keystrokes 
int findoptimal(int N) 
{ 
    // The optimal string length is N when N is smaller than 7 
    if (N <= 6) 
        return N; 
  
    // Initialize result 
    int max = 0; 
  
    // TRY ALL POSSIBLE BREAK-POINTS 
    // For any keystroke N, we need to loop from N-3 keystrokes 
    // back to 1 keystroke to find a breakpoint 'b' after which we 
    // will have Ctrl-A, Ctrl-C and then only Ctrl-V all the way. 
    int b; 
    for (b = N - 3; b >= 1; b--) { 
        // If the breakpoint is s at b'th keystroke then 
        // the optimal string would have length 
        // (n-b-1)*screen[b-1]; 
        
        int curr = (N - b - 1) * findoptimal(b); 
        if (curr > max) 
            max = curr; 
        if (N==11){
                printf("%d == %d\n", b, curr);
        }    
    } 
    
    return max; 
} 
  
// Driver program 
int main() 
{ 
    int N; 
  
    // for the rest of the array we will rely on the previous 
    // entries to compute new ones 
    for (N = 1; N <= 20; N++) 
        printf("Maximum Number of A's with %d keystrokes is %d\n", 
               N, findoptimal(N)); 
}