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Optimize day 23 by moving three cups at a time

master
Nick Krichevsky 2020-12-27 04:24:21 -05:00
parent 887250978e
commit 4abe71ccf5
1 changed files with 53 additions and 4 deletions
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57
day23/day23.cpp
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@ -138,6 +138,9 @@ class CupGraph {
/** /**
* Move the cup at key to be clockwise to dest * Move the cup at key to be clockwise to dest
*
* **This is not used in the final solution, but is kept for posterity**
*
* @param key The cup to move * @param key The cup to move
* @param dest The cup that will be counterclockwise to key (i.e. key will be clockwise to dest) * @param dest The cup that will be counterclockwise to key (i.e. key will be clockwise to dest)
*/ */
@ -170,6 +173,53 @@ class CupGraph {
this->neighbors.left.insert({dest, key}); this->neighbors.left.insert({dest, key});
} }
/**
* The same as move, but moves key, key's neighbor, and key's neighbor's neighbor, at once
* @param key The key to move
* @param dest The destination to move to
*/
void move3(int key, int dest) {
auto keyIt = this->neighbors.left.find(key);
auto destIt = this->neighbors.left.find(dest);
if (keyIt == this->neighbors.left.end() || destIt == this->neighbors.left.end()) {
throw std::out_of_range("Item not in map");
}
// Get the two elements after the key.
auto keyIt2 = this->neighbors.left.find(keyIt->second);
if (keyIt2 == this->neighbors.left.end()) {
throw "Invalid state: elements are not linked together";
}
auto keyIt3 = this->neighbors.left.find(keyIt2->second);
if (keyIt3 == this->neighbors.left.end()) {
throw "Invalid state: elements are not linked together";
}
auto counterclockwiseFromKeyIt = this->neighbors.right.find(key);
if (counterclockwiseFromKeyIt == this->neighbors.right.end()) {
throw std::invalid_argument("Key has no counterclockwise neighbor");
}
int key3 = keyIt3->first;
int clockwiseFromKey3 = keyIt3->second;
int clockwiseFromDest = destIt->second;
int counterclockwiseFromKey = counterclockwiseFromKeyIt->second;
// Unfortunately, using replace doesn't work because we expect that each side has exactly one of each element,
// so doing this shuffle is not possible with replace, without some serious edgecasing.
this->neighbors.right.erase(key);
this->neighbors.left.erase(key3);
// this->neighbors.left.erase(key);
this->neighbors.left.erase(dest);
// Stitch the counterclockwise neighbor to be the one clockwise to the final element in our range
this->neighbors.left.insert({counterclockwiseFromKey, clockwiseFromKey3});
// Stitching the final element of our range to have the same neighbor as the destination did
this->neighbors.left.insert({key3, clockwiseFromDest});
// Stitch the destination to be adjacent to the key
this->neighbors.left.insert({dest, key});
}
/** /**
* Get the neighbor of this element * Get the neighbor of this element
* @param n The item to get the neighbor * @param n The item to get the neighbor
@ -316,11 +366,10 @@ void runGame(int startingCup, CupGraph &graph, int numIterations) {
int currentCup = startingCup; int currentCup = startingCup;
for (int i = 0; i < numIterations; i++) { for (int i = 0; i < numIterations; i++) {
int destinationCup = findDestinationCup(currentCup, graph, cupMinMax.first, cupMinMax.second); int destinationCup = findDestinationCup(currentCup, graph, cupMinMax.first, cupMinMax.second);
std::tuple<int, int, int> pickedUpCups = getPickedUpCups(currentCup, graph);
graph.move(std::get<0>(pickedUpCups), destinationCup); // Since we move three at a time, we only need to get the first picked up cup
graph.move(std::get<1>(pickedUpCups), std::get<0>(pickedUpCups)); int firstPickedUpCup = graph.getNext(currentCup);
graph.move(std::get<2>(pickedUpCups), std::get<1>(pickedUpCups)); graph.move3(graph.getNext(currentCup), destinationCup);
currentCup = graph.getNext(currentCup); currentCup = graph.getNext(currentCup);
} }