Add day 1 solution

Author: JPry

ts/index.ts

@@ -10,6 +10,80 @@ type DayInput = string;
 type DaySolver = (input: DayInput) => void;
 
 const daySolvers: { [key: string]: DaySolver } = {
+    '01': (input: DayInput) => {
+        let zeroCount1: number = 0;
+        let zeroCount2: number = 0;
+        let currentPosition: number = 50;
+        let newPosition: number;
+        const splitInput = input.split("\n").filter((line) => line.trim() !== '');
+
+        splitInput.forEach((line: string) => {
+            const matches = line.match(/([R|L])(\d+)/) || [];
+
+            if (matches.length < 3) {
+                console.warn(`Invalid instruction: ${line}`);
+                return;
+            }
+
+            const direction = matches[1];
+            const distance = parseInt(matches[2], 10);
+            let revolutions = Math.floor(distance / 100);
+            const remainder = distance % 100;
+
+            /*
+             * Part 2 Logic:
+             *
+             * We need to track how many times we cross position 0.
+             * Each full revolution (100 units) guarantees crossing position 0 once.
+             * Therefore, for every full revolution in the distance, we increment zeroCount2 by 1.
+             * After accounting for full revolutions, we check the remainder distance to see if it crosses position 0.
+             *
+             *
+             * When moving right (R):
+             * - If the current position + distance crosses or lands on 0, increment zeroCount2.
+             *
+             * When moving left (L):
+             * - If the current position - distance crosses or lands on 0, increment zeroCount2.
+             * - Starting position of 1, moving left 1 lands on 0 (crosses once).
+             * - Starting position of 1, moving left 150 lands on 51, crosses 0 twice (once at 0 and once more after a full revolution).
+             */
+
+            switch (direction) {
+                case 'R':
+                    newPosition = currentPosition + remainder;
+                    if (newPosition === 100) {
+                        newPosition = 0;
+                    } else if (newPosition > 100) {
+                        newPosition = newPosition % 100;
+                        revolutions++;
+                    }
+                    break;
+                case 'L':
+                    newPosition = currentPosition - remainder;
+                    if (newPosition < 0) {
+                        newPosition += 100;
+                        if (currentPosition !== 0) {
+                            revolutions++;
+                        }
+                    }
+                    break;
+                default:
+                    throw new Error(`Unknown direction: ${direction}`);
+            }
+
+            zeroCount2 += revolutions;
+            currentPosition = newPosition;
+
+            if (currentPosition === 0) {
+                zeroCount1++;
+                zeroCount2++;
+                return;
+            }
+        });
+
+        console.log(`Part 1: Number of times position 0 was reached: ${zeroCount1}`);
+        console.log(`Part 2: Number of times position 0 was crossed: ${zeroCount2}`);
+    },
 };
 
 // Set up the CLI program.