.

2021/3.js

@@ -0,0 +1,21 @@
+function day3(input, part2) {
+    let g = Grid.fromStr(input)
+
+    if (!part2) {
+        let gamma = g.getColumns().map((col) => col.mode())
+        let epsilon = g.getColumns().map((col) => col.antimode())
+        return parseInt(gamma.join``, 2) * parseInt(epsilon.join``, 2)
+    } else {
+        let oxy = g.getRows()
+        let co2 = g.getRows()
+
+        for (let i = 0; i < g.width; i++) {
+            let oxyBit = oxy.transpose()[i].mode((a, b) => a == 1 ? -1 : 1)
+            let co2Bit = co2.transpose()[i].antimode((a, b) => a == 0 ? -1 : 1)
+            oxy = oxy.filter((e) => e[i] == oxyBit)
+            co2 = co2.filter((e) => e[i] == co2Bit)
+        }
+
+        return parseInt(oxy[0].join``, 2) * parseInt(co2[0].join``, 2)
+    }
+}

2021/4.js

@@ -0,0 +1,34 @@
+function day4(input, part2) {
+    input = input.split("\n")
+
+    let seq = input.shift().split(",").num()
+    let grids = input.splitOnElement("").filter((e) => e.length).map((grid) => Grid.fromStr(grid.map((line) => line.replace(/^ /, "")).join("\n"), /\s+/).mapMut((e) => [+e, false]))
+
+    let score
+
+    for (let num of seq) {
+        for (let grid of grids) {
+            if (grid.won) {
+                continue
+            }
+
+            let pt = grid.findIndex((e) => e[0] == num)
+
+            if (pt == Point.NONE) {
+                continue
+            }
+
+            grid.set(pt, [num, true])
+
+            if ([...grid.getRows(), ...grid.getColumns()].some((row) => row.every((e) => e[1]))) {
+                grid.won = true
+
+                if (!score || part2) {
+                    score = grid.findAll((e) => !e[1]).map((e) => e[0]).sum() * num
+                }
+            }
+        }
+    }
+
+    return score
+}