The Snoring Giant of Hobbenfell

Posted by the Lantern Guild of Hobbenfell. High on Hobbenfell ridge, the giant Gorrund sleeps in his hall beside a table heaped with gold coins. A band of thieves will slip in and carry out a fixed list of moves, one after another. Before anyone risks their neck, the Guild wants a reckoning: how much gold comes home, and whether Gorrund wakes.

Write giantHeist(actions, hoard).

• actions is a list of strings, each exactly "grab", "stash" or "wait", in the order they are performed.
• hoard is a non-negative integer: the number of coins on the table at the start.

The raid has this state:

• the giant's restlessness, which starts at 0;
• the sack, which starts empty and can hold at most 3 coins;
• the stash by the door, which starts at 0 coins.

Process the actions in order. For each action:

1. The giant is lightly asleep if his restlessness is at least 4 at that moment, before this action. Otherwise he is deeply asleep. 2. The action's base noise is: - "grab": 2, or 3 if the action immediately before it in the list was also "grab"; - "stash": 1; - "wait": 0. If the giant is lightly asleep, the noise is doubled. 3. Add the noise to his restlessness. If his restlessness is now 9 or more, he wakes: this action does not take effect, every coin in the sack is lost, and all remaining actions are ignored. 4. Otherwise the action takes effect: - "grab": if the sack holds fewer than 3 coins and the table still has a coin, move one coin from the table into the sack. Otherwise no coin moves. Either way the action still made its noise and still counts as a grab for the action after it. - "stash": move every coin in the sack to the stash; the sack becomes empty. - "wait": reduce his restlessness by 3, but not below 0.

Return a list of two integers [coins, woke]:

• coins is the number of coins in the stash, plus the coins in the sack if the giant never woke. If he woke, sack coins do not count.
• woke is the 0-based index of the action that woke the giant, or -1 if he slept through every action.