From c066cf155d17d885561d6ccc07c870f2841bebf6 Mon Sep 17 00:00:00 2001
From: Anna Wiggins <annabunches@gmail.com>
Date: Sat, 1 Dec 2018 21:40:48 -0500
Subject: [PATCH] Day 1 completed.

---
 2018/day01.go | 56 +++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 56 insertions(+)
 create mode 100644 2018/day01.go

diff --git a/2018/day01.go b/2018/day01.go
new file mode 100644
index 0000000..fa4e26d
--- /dev/null
+++ b/2018/day01.go
@@ -0,0 +1,56 @@
+package main
+
+import (
+	"bufio"
+	"fmt"
+	"os"
+	"strconv"
+)
+
+type Set map[int]struct{}
+
+// Provide a filename as input, get the result on stdout
+func main() {
+	x := 0
+	found := false
+	seen := Set{0: struct{}{}}
+
+	for {
+		x, found = ScanFrequencies(os.Args[1], &seen, x)
+		if found {
+			break
+		}
+		fmt.Println("All frequencies scanned, repeating...")
+	}
+
+	fmt.Println("Repeat frequency detected, calibration complete: ", x)
+}
+
+// ScanFrequencies iterates over a list of frequencies (provided as an open
+// file handle), compares against a list of frequencies already seen and a 'current' frequency counter,
+// and returns `true` when a duplicate frequency is found. Integer value returned is the new, adjusted frequency
+func ScanFrequencies(freqFile string, seen *Set, frequency int) (int, bool) {
+	file, err := os.Open(os.Args[1])
+	if err != nil {
+		panic(err)
+	}
+
+	duplicateFound := false
+	scanner := bufio.NewScanner(file)
+	for scanner.Scan() {
+		y, err := strconv.Atoi(scanner.Text())
+		if err != nil {
+			panic(err)
+		}
+		frequency += y
+		if _, ok := (*seen)[frequency]; ok {
+			duplicateFound = true
+			break
+		}
+
+		(*seen)[frequency] = struct{}{}
+	}
+
+	file.Close()
+	return frequency, duplicateFound
+}