.

2021/9.js

@@ -0,0 +1,15 @@
+function day9(input, part2) {
+    let grid = Grid.fromStr(input).num()
+
+    let lows = grid.findAllIndices((e, pt, g) => g.getAdjNeighbors(pt).every((nb) => e < g.get(nb)))
+
+    if (!part2) {
+        return lows.map((e) => grid.get(e) + 1).sum()
+    }
+
+    let sizes = lows.map((low) => grid.bfs(low, (e, pt, g) => {
+        return e == 9 || g.get(pt.path.last) < e ? Grid.BFS_STOP : Grid.BFS_CONTINUE
+    }).filter((e) => e.result == Grid.BFS_CONTINUE).length).sort((a, b) => b - a)
+
+    return sizes[0] * sizes[1] * sizes[2]
+}