day 13!

puzzles/2024/day12/solution.ts

@@ -39,6 +39,27 @@ const floodFill = (grid: string[], details: { area: number, perimeter: { [key: s
     if (x !== width - 1 && grid[y][x + 1] === plant) floodFill(grid, details, x + 1, y, area);
 }
 
+/**
+ * remove extra perimeter based on axis
+ */
+const filterPerimeters = (array: Perimeter[], primary: 'x' | 'y', secondary: 'x' | 'y') => {
+    // sort from smallest to largest
+    array.sort((a, b) => a[primary] - b[primary]);
+
+    // try to remove any perimeters on the same line
+    for (let i = 0; i < array.length; i++) {
+        let check = array[i][primary];
+        while (true) {
+            check++;
+            const nextNode = array.find(node => node[primary] === check && node[secondary] === array[i][secondary]);
+
+            // end check if not on continuous line
+            if (nextNode !== undefined) nextNode.valid = false;
+            else break;
+        }
+    }
+}
+
 /**
  * the code of part 1 of the puzzle
  */
@@ -73,27 +94,6 @@ const part2 = (input: string) => {
     const grid = input.trim().split('\n');
     const width = grid[0].length, height = grid.length;
 
-    /**
-     * remove extra perimeter based on axis
-     */
-    const filterPerimeters = (array: Perimeter[], primary: 'x' | 'y', secondary: 'x' | 'y') => {
-        // sort from smallest to largest
-        array.sort((a, b) => a[primary] - b[primary]);
-
-        // try to remove any perimeters on the same line
-        for (let i = 0; i < array.length; i++) {
-            let check = array[i][primary];
-            while (true) {
-                check++;
-                const nextNode = array.find(node => node[primary] === check && node[secondary] === array[i][secondary]);
-
-                // end check if not on continuous line
-                if (nextNode !== undefined) nextNode.valid = false;
-                else break;
-            }
-        }
-    }
-
     let alreadyFlooded = new Set<string>();
     let sum = 0;
     for (let y = 0; y < height; y++) {

puzzles/2024/day13/README.md

@@ -0,0 +1,29 @@
+# Advent of Code 2024 - Day 13: [Claw Contraption](https://adventofcode.com/2024/day/13)
+
+## [Write Up](https://codingap.github.io/advent-of-code/writeups/2024/day13)
+
+## Results
+
+|                  | **Part 1** | **Part 2** |
+| :--------------: | :--------: | :--------: |
+|   **Results**    | 28753 | 9144671599845478000 |
+| **Time (in ms)** | 1.49 | 2.05 |
+
+%%%
+
+Leaderboard Positions - **Part 1**: 2316, **Part 2**: 679
+
+[Video Replay](https://youtu.be/6QdOUQeiPCk)
+
+Hello all! In this puzzle, we are trying to figure out the exact number of button presses to reach a goal in a crane machine. Each crane has two buttons labeled `A` and `B`, which both buttons advancing the crane arm a specific amount. We need to find how many of each button press will lead to the position being exactly the goal. In part 1, we try to find the amount, then add all the successful `A` and `B` numbers with this formula: `3 * A + B`. To prevent bruteforcing, we treat each button as a system of linear equations, which we can solve as there are two variables and two equation. I made a [Desmos](https://www.desmos.com/calculator/l1amw7m2rg) that calculates the `A` and `B` given the constants. To map the constant for completion sake:
+
+```
+c1: button a x
+c2: button b x
+c3: prize x
+c4: button a y
+c5: button b y
+c6: prize y
+```
+
+For part 2, we need to add `10000000000000` to each of the prize positions, which with our current solution shouldn't be a problem. One thing to note is make sure to keep floating point inaccuracies down, so do as much integer arithetic as possible

puzzles/2024/day13/solution.ts

@@ -0,0 +1,63 @@
+/**
+ * puzzles/2024/day13/solution.ts
+ *
+ * ~~ Claw Contraption ~~
+ * this is my solution for this advent of code puzzle
+ *
+ * by alex prosser
+ * 12/12/2024
+ */
+
+/**
+ * the code of part 1 of the puzzle
+ */
+const part1 = (input: string) => {
+    // parse the constants out of each test
+    const machines = input.trim().split('\n\n').map(lines => {
+        const [buttonA, buttonB, prize] = lines.split('\n');
+        const [c1, c4] = buttonA.split(': ')[1].split(', ').map(num => parseInt(num.split('+')[1]));
+        const [c2, c5] = buttonB.split(': ')[1].split(', ').map(num => parseInt(num.split('+')[1]));
+        const [c3, c6] = prize.split(': ')[1].split(', ').map(num => parseInt(num.split('=')[1]));
+        return { c1, c2, c3, c4, c5, c6 };
+    });
+
+    return machines.reduce((sum, machine, i) => {
+        // try to calculate a and b
+        // c3 = c1 * a + c2 * b
+        // c6 = c4 * a + c5 * b
+        // https://www.desmos.com/calculator/l1amw7m2rg
+        const b = (machine.c1 * machine.c6 - machine.c4 * machine.c3) / (machine.c1 * machine.c5 - machine.c4 * machine.c2);
+        const a = (machine.c3 - machine.c2 * b) / machine.c1;
+
+        // test is accepted when both numbers are integers
+        return sum + ((a % 1 === 0 && b % 1 === 0) ? (a * 3 + b) : 0);
+    }, 0);
+};
+
+/**
+ * the code of part 2 of the puzzle
+ */
+const part2 = (input: string) => {
+    // parse the constants out of each machine, add 10000000000000 to the prize position
+    const machines = input.trim().split('\n\n').map(lines => {
+        const [buttonA, buttonB, prize] = lines.split('\n');
+        const [c1, c4] = buttonA.split(': ')[1].split(', ').map(num => parseInt(num.split('+')[1]));
+        const [c2, c5] = buttonB.split(': ')[1].split(', ').map(num => parseInt(num.split('+')[1]));
+        const [c3, c6] = prize.split(': ')[1].split(', ').map(num => parseInt(num.split('=')[1]) + 10000000000000);
+        return { c1, c2, c3, c4, c5, c6 };
+    });
+
+    return machines.reduce((sum, machine) => {
+        // try to calculate a and b
+        // c3 = c1 * a + c2 * b
+        // c6 = c4 * a + c5 * b
+        // https://www.desmos.com/calculator/l1amw7m2rg
+        const b = (machine.c1 * machine.c6 - machine.c4 * machine.c3) / (machine.c1 * machine.c5 - machine.c4 * machine.c2);
+        const a = (machine.c3 - machine.c2 * b) / machine.c1;
+
+        // test is accepted when both numbers are integers
+        return sum + ((a % 1 === 0 && b % 1 === 0) ? (a * 3 + b) : 0);
+    }, 0);
+};
+
+export { part1, part2 };