From c980fdf735f40b8f3b86691a9aee1277d1f6137d Mon Sep 17 00:00:00 2001
From: Nick Krichevsky <nick@ollien.com>
Date: Sun, 27 Dec 2020 14:36:29 -0500
Subject: [PATCH] Refactor move to take a number of cups to move in day 23

---
 day23/day23.cpp | 73 ++++++++++++-------------------------------------
 1 file changed, 17 insertions(+), 56 deletions(-)

diff --git a/day23/day23.cpp b/day23/day23.cpp
index e319498..98ba3e9 100644
--- a/day23/day23.cpp
+++ b/day23/day23.cpp
@@ -131,86 +131,45 @@ class CupGraph {
 			CupGraph::const_iterator(*this, start), CupGraph::const_iterator(*this, CupGraph::const_iterator::END));
 	}
 
-	/**
-	 * 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 dest The cup that will be counterclockwise to key (i.e. key will be clockwise to dest)
-	 */
-	void move(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");
-		}
-
-		auto counterclockwiseFromKeyIt = this->neighbors.right.find(key);
-		if (counterclockwiseFromKeyIt == this->neighbors.right.end()) {
-			throw std::invalid_argument("Key has no counterclockwise neighbor");
-		}
-
-		int clockwiseFromKey = keyIt->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(key);
-		this->neighbors.left.erase(dest);
-
-		// Stitch the counterclockwise neighbor to be the one clockwise to keyIt
-		this->neighbors.left.insert({counterclockwiseFromKey, clockwiseFromKey});
-		// Stitching the key to have the same neighbor as the destination did
-		this->neighbors.left.insert({key, clockwiseFromDest});
-		// Stitch the destination to be adjacent to the 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) {
+	void move(int key, int dest, int numToMove) {
 		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;
+		auto endOfRangeIt = keyIt;
+		for (int i = 1; i < numToMove; i++) {
+			endOfRangeIt = this->neighbors.left.find(endOfRangeIt->second);
+			if (endOfRangeIt == this->neighbors.left.end()) {
+				throw "Invalid state: elements are not linked together";
+			}
+		}
+
+		int endOfRangeKey = endOfRangeIt->first;
+		int clockwiseFromEndOfRangeKey = endOfRangeIt->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(endOfRangeKey);
 		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});
+		this->neighbors.left.insert({counterclockwiseFromKey, clockwiseFromEndOfRangeKey});
 		// Stitching the final element of our range to have the same neighbor as the destination did
-		this->neighbors.left.insert({key3, clockwiseFromDest});
+		this->neighbors.left.insert({endOfRangeKey, clockwiseFromDest});
 		// Stitch the destination to be adjacent to the key
 		this->neighbors.left.insert({dest, key});
 	}
@@ -362,7 +321,9 @@ void runGame(int startingCup, CupGraph &graph, int numIterations) {
 
 		// Since we move three at a time, we only need to get the first picked up cup
 		int firstPickedUpCup = graph.getNext(currentCup);
-		graph.move3(firstPickedUpCup, destinationCup);
+		using tupleType = typename std::result_of<decltype (&getPickedUpCups)(int, const CupGraph &)>::type;
+		constexpr auto numCupsToMove = std::tuple_size<tupleType>::value;
+		graph.move(firstPickedUpCup, destinationCup, numCupsToMove);
 
 		currentCup = graph.getNext(currentCup);
 	}