d01

day01/d01p2.swift

@@ -0,0 +1,21 @@
+import Foundation
+
+func readInput(filePath: String) -> ([Int], [Int]) {
+    let content =  try? String(contentsOfFile: filePath, encoding: .ascii)
+    let lines = content!.split(separator: "\n")
+    var leftList: [Int] = []
+    var rightList: [Int] = []
+    for line in lines {
+        let lr = line.split(separator: " ")
+        leftList.append(Int(lr[0])!)
+        rightList.append(Int(lr[1])!)
+    }
+    return (leftList, rightList)
+}
+
+let (leftList, rightList) = readInput(filePath: CommandLine.arguments[1])
+var counts: [Int: Int] = [:]
+for n in rightList {
+    counts[n, default: 0] += 1
+}
+print(leftList.reduce(0, { sum, n in sum + n * counts[n, default: 0] }))