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Return to Printing A.
Imagine you have a special keyboard with the following keys:
A
Ctrl+A
Ctrl+C Ctrl+V where CTRL+A, CTRL+C, CTRL+V each acts as one function key for “Select All”, “Copy”, and “Paste” operations respectively. If you can only press the keyboard for N times (with the above four keys), please write a program to produce maximum numbers of A. If possible, please also print out the sequence of keys. That is to say, the input parameter is N (No. of keys that you can press), the output is M (No. of As that you can produce).
<syntaxhighlight lang="c" name="printa">
int main() {
unsigned long N, M, i; printf("Enter N: "); scanf("%lu", &N); if(N <= 6) { M = 6; for(i = 0; i < N; i++) printf("A\n"); } else if (N % 3 == 0) { M = 3 * (1L<< (N-3)/3); //1<<x gives pow(2,x) and I'm too lazy to include math.h for(i = 0; i < 3; i++) printf("A\n"); for(i = 1; i < N/3; i++) { printf("Select\n"); printf("Copy\n"); printf("Paste\n"); } } else { M = 4 * (1L << (N-4)/3) + (N-4)%3; //1<<x gives pow(2,x) for(i = 0; i < 4; i++) printf("A\n"); for(i=0; i < (N-4)/3; i++) { printf("Select\n"); printf("Copy\n"); printf("Paste\n"); } for(i = 0; i < N%3; i++) printf("A\n"); } printf("\nM = %lu\n", M);
} </syntaxhighlight>