AoC2025: day 5 part 2

Author: martapanc

2024-2025/src/2025/day05/day05.test.ts

@@ -8,6 +8,6 @@ describe('2025 Day 5', () => {
 
     test('Part 2', async () => {
         expect(await part2('testInput1')).toEqual(14);
-        expect(await part2('input')).toEqual(1111);
+        expect(await part2('input')).toEqual(345821388687084);
     });
 });

2024-2025/src/2025/day05/day05.ts

@@ -46,55 +46,17 @@ function findFreshIngredients(idRanges: IdRange[], ingredientIds: number[]): num
 }
 
 function findTotalFreshIngredientCount(idRanges: IdRange[], _: number[]): number {
-    let reduceRanges = true;
-    let idRangesCopy = idRanges.slice();
+    const sorted = idRanges.slice().sort((a, b) => a.from - b.from);
+    const merged: IdRange[] = [];
 
-    while (reduceRanges) {
-        reduceRanges = false;
-        for (let i = 0; i < idRanges.length; i++){
-            const a = idRanges[i];
-            for (let j = i + 1; j < idRanges.length; j++) {
-                const b = idRanges[j];
-
-                if (a.from >= b.from && a.from <= b.to) {
-                    reduceRanges = true;
-                    idRangesCopy.splice(j, 1);
-                    idRangesCopy.splice(i, 1);
-                    if (a.to >= b.to) {
-                        idRangesCopy.push({ from: b.from, to: a.to });
-                    }
-                    if (b.to >= a.to) {
-                        idRangesCopy.push({ from: b.from, to: b.to });
-                    }
-                    break;
-                }
-
-                if (a.to >= b.from && a.to <= b.to) {
-                    reduceRanges = true;
-                    idRangesCopy.splice(j, 1);
-                    idRangesCopy.splice(i, 1);
-
-                    if (a.from >= b.from) {
-                        idRangesCopy.push({ from: b.from, to: b.to });
-                    }
-                    if (b.from >= a.from) {
-                        idRangesCopy.push({ from: a.from, to: b.to });
-                    }
-                    break;
-                }
-            }
-            if (reduceRanges) {
-                break;
-            }
+    for (const range of sorted) {
+        const last = merged[merged.length - 1];
+        if (last && range.from <= last.to + 1) {
+            last.to = Math.max(last.to, range.to);
+        } else {
+            merged.push({ ...range });
         }
-
-        idRanges = idRangesCopy.slice();
     }
 
-    let freshCount = 0;
-    idRanges.forEach(idRange => {
-        freshCount += (idRange.to - idRange.from) + 1;
-    })
-
-    return freshCount;
+    return merged.reduce((sum, r) => sum + (r.to - r.from + 1), 0);
 }