Black Jack
Problem
Input contains a sequence of integers that represent values of a deck of cards. Read an input and add it to the previous input. Print the new sum if it is as close to 21 as possible, while being at most 21.
Solution 1
Let the register int store the cumulative sum. Assume the register initially
holds zero. We read a value into reg, update the cumulative sum
int := reg + int
and determine whether the updated cumulative sum is greater than 21. If the
value of int is at most 21, read in the next value. Otherwise, the value of
int is greater than 21 and we know that the newly read input value contributes
to this updated sum. Revert to the previous value of int and print the
previous value. Finally, assign the new input value to int. Continue the above
process until we have no more values to read, at which point we simply print
whatever value is held in int.
loop: // Start of "loop".
check input = null; // Any more numbers?
jump if true: end; // If no more, go to "end".
reg = input; // Otherwise, read next value.
int = reg + int; // Update cumulative sum.
check int > 21; // Is sum > 21?
jump if false: loop; // If not, go to "loop".
int = int - reg; // Otherwise, use previous value.
output = int; // Print the previous value.
int = reg; // Now start with current input.
jump to: loop; // Go to "loop".
end: // The "end" branch.
output = int; // Print whatever is in "int".
Solution 2
Similar to Solution 1. However, we remove a jump instruction and use only one print statement. This solution is optimal, according to the game.
loop: // Start of "loop".
check input = null; // Any more numbers?
jump if true: print; // If no more, go to "print".
reg = input; // Otherwise, read next value.
int = reg + int; // Update cumulative sum.
check int > 21; // Is sum > 21?
jump if false: loop; // If not, go to "loop".
int = int - reg; // Otherwise, use previous value.
print: // The "print" branch.
output = int; // Print whatever is in "int".
int = reg; // Now start with current input.