day 13 + 14

day14/main.swift

@@ -0,0 +1,92 @@
+import Foundation
+let scanner = Scanner(string: loadData(day: 14))
+
+
+var maskBits: UInt64 = 0
+var maskUsed: UInt64 = 0
+
+
+var mem: [UInt64:UInt64] = [:]
+
+
+func readMask(_ mask: String) {
+    assert(mask.count == 36)
+
+    maskBits = 0
+    maskUsed = 0
+
+    for char in mask {
+        maskBits <<= 1
+        maskUsed <<= 1
+
+        switch char {
+        case "1": maskBits |= 1
+        case "0": break
+        case "X": maskUsed |= 1
+        default: assertionFailure("Invalid character in mask")
+        }
+    }
+}
+
+func applyMask(_ value: UInt64) -> UInt64 {
+    (value & maskUsed) | maskBits
+}
+
+let maskSet = CharacterSet(charactersIn: "01X")
+
+/*
+while !scanner.isAtEnd {
+    if scanner.string("mask = "), let mask = scanner.scanCharacters(from: maskSet) {
+        readMask(mask)
+    } else if scanner.string("mem["), let addr = scanner.scanInt(), scanner.string("] = "), let value = scanner.scanUInt64() {
+        mem[addr] = applyMask(value)
+    } else {
+        assertionFailure("Invalid input")
+    }
+}
+ */
+
+
+func printPadded(_ val: UInt64) {
+    let s = String(val, radix: 2)
+    print(String(repeating: " ", count: 36 - s.count) + s)
+}
+
+func possibleValues(_ mask: UInt64) -> [UInt64] {
+    var values: [UInt64] = []
+    var mask = mask
+    for i in 0..<36 {
+        if mask & 1 != 0 {
+            let bit: UInt64 = 1 << i
+            if values.isEmpty {
+                values.append(0)
+                values.append(bit)
+            } else {
+                values.append(contentsOf: values.map { $0 | bit })
+            }
+        }
+        mask >>= 1
+    }
+
+    return values
+}
+
+func writeMem(_ addr: UInt64, _ value: UInt64) {
+    for i in possibleValues(maskUsed) {
+        let effective = i | ((addr | maskBits) & ~maskUsed)
+        mem[effective] = value
+    }
+}
+
+while !scanner.isAtEnd {
+    if scanner.string("mask = "), let mask = scanner.scanCharacters(from: maskSet) {
+        readMask(mask)
+    } else if scanner.string("mem["), let addr = scanner.scanUInt64(), scanner.string("] = "), let value = scanner.scanUInt64() {
+        writeMem(addr, value)
+    } else {
+        assertionFailure("Invalid input")
+    }
+}
+
+
+print("sum", mem.values.reduce(0, +))