Day 4 done

day4/main.go

@@ -0,0 +1,190 @@
+package main
+
+import (
+	"fmt"
+	"os"
+)
+
+func main() {
+	if len(os.Args) < 2 {
+		panic("Provide input file")
+	}
+	inputFile := os.Args[1]
+
+	part1 := part1(inputFile)
+	fmt.Printf("(%s) Part 1: %d\n", inputFile, part1)
+
+	part2 := part2(inputFile)
+	fmt.Printf("(%s) Part 2: %d\n", inputFile, part2)
+}
+
+func part2(inputFile string) int {
+	input, err := os.Open(inputFile)
+	if err != nil {
+		panic(err)
+	}
+	defer input.Close()
+
+	wordSearch := make([][]rune, 0)
+	row := 0
+	for {
+		var line string
+		_, err := fmt.Fscanf(input, "%s\n", &line)
+		if err != nil {
+			break
+		}
+
+		wordSearch = append(wordSearch, make([]rune, len(line)))
+		for i, c := range line {
+			wordSearch[row][i] = c
+		}
+		row++
+	}
+
+	return crossSearchMap(wordSearch)
+}
+
+func crossSearchMap(wordSearch [][]rune) int {
+	possibilities := make([][]int, len(wordSearch))
+	for i := range possibilities {
+		possibilities[i] = make([]int, len(wordSearch[i]))
+	}
+
+	count := 0
+	for y, row := range wordSearch {
+		for x, c := range row {
+			if c == 'A' {
+				if crossCheck(wordSearch, x, y) {
+					count++
+				}
+			}
+		}
+	}
+	return count
+}
+
+func crossCheck(wordSearch [][]rune, x, y int) bool {
+	downLeft := false
+	downRight := false
+	if y-1 >= 0 && y+1 < len(wordSearch) && x-1 >= 0 && x+1 < len(wordSearch[y]) {
+		fmt.Printf("Checking cross at %d,%d\n", x, y)
+		fmt.Printf("Checking %c %c\n", wordSearch[y-1][x-1], wordSearch[y+1][x+1])
+		if wordSearch[y-1][x-1] == 'M' && wordSearch[y+1][x+1] == 'S' {
+			downLeft = true
+		} else if wordSearch[y-1][x-1] == 'S' && wordSearch[y+1][x+1] == 'M' {
+			downLeft = true
+		}
+		fmt.Printf("Checking %c %c\n", wordSearch[y+1][x-1], wordSearch[y-1][x+1])
+		if wordSearch[y-1][x+1] == 'M' && wordSearch[y+1][x-1] == 'S' {
+			downRight = true
+		} else if wordSearch[y-1][x+1] == 'S' && wordSearch[y+1][x-1] == 'M' {
+			downRight = true
+		}
+	}
+	if downLeft && downRight {
+		return true
+	}
+	return false
+}
+
+func part1(inputFile string) int {
+	input, err := os.Open(inputFile)
+	if err != nil {
+		panic(err)
+	}
+	defer input.Close()
+
+	wordSearch := make([][]rune, 0)
+	row := 0
+	for {
+		var line string
+		_, err := fmt.Fscanf(input, "%s\n", &line)
+		if err != nil {
+			break
+		}
+
+		wordSearch = append(wordSearch, make([]rune, len(line)))
+		for i, c := range line {
+			wordSearch[row][i] = c
+		}
+		row++
+	}
+
+	return searchMap(wordSearch)
+}
+
+// finds X's and then calls xmas to see if it makes 'XMAS'
+func searchMap(wordSearch [][]rune) int {
+	count := 0
+	for y, row := range wordSearch {
+		for x, c := range row {
+			if c == 'X' {
+				count += xmas(wordSearch, x, y)
+			}
+		}
+	}
+	return count
+}
+
+func xmas(wordSearch [][]rune, x, y int) int {
+	count := 0
+
+	// fmt.Printf("Checking XMAS at %d,%d\n", x, y)
+	// check up
+	if y-3 >= 0 {
+		// fmt.Printf("Checking %c %c %c\n", wordSearch[y-1][x], wordSearch[y-2][x], wordSearch[y-3][x])
+		if wordSearch[y-1][x] == 'M' && wordSearch[y-2][x] == 'A' && wordSearch[y-3][x] == 'S' {
+			count++
+		}
+	}
+	// check up-left
+	if y-3 >= 0 && x-3 >= 0 {
+		// fmt.Printf("Checking %c %c %c\n", wordSearch[y-1][x-1], wordSearch[y-2][x-2], wordSearch[y-3][x-3])
+		if wordSearch[y-1][x-1] == 'M' && wordSearch[y-2][x-2] == 'A' && wordSearch[y-3][x-3] == 'S' {
+			count++
+		}
+	}
+	// check left
+	if x-3 >= 0 {
+		// fmt.Printf("Checking %c %c %c\n", wordSearch[y][x-1], wordSearch[y][x-2], wordSearch[y][x-3])
+		if wordSearch[y][x-1] == 'M' && wordSearch[y][x-2] == 'A' && wordSearch[y][x-3] == 'S' {
+			count++
+		}
+	}
+	// check down-left
+	if y+3 < len(wordSearch) && x-3 >= 0 {
+		// fmt.Printf("Checking %c %c %c\n", wordSearch[y+1][x-1], wordSearch[y+2][x-2], wordSearch[y+3][x-3])
+		if wordSearch[y+1][x-1] == 'M' && wordSearch[y+2][x-2] == 'A' && wordSearch[y+3][x-3] == 'S' {
+			count++
+		}
+	}
+	// check down
+	if y+3 < len(wordSearch) {
+		// fmt.Printf("Checking %c %c %c\n", wordSearch[y+1][x], wordSearch[y+2][x], wordSearch[y+3][x])
+		if wordSearch[y+1][x] == 'M' && wordSearch[y+2][x] == 'A' && wordSearch[y+3][x] == 'S' {
+			count++
+		}
+	}
+	// check down-right
+	if y+3 < len(wordSearch) && x+3 < len(wordSearch[y]) {
+		// fmt.Printf("Checking %c %c %c\n", wordSearch[y+1][x+1], wordSearch[y+2][x+2], wordSearch[y+3][x+3])
+		if wordSearch[y+1][x+1] == 'M' && wordSearch[y+2][x+2] == 'A' && wordSearch[y+3][x+3] == 'S' {
+			count++
+		}
+	}
+	// check right
+	if x+3 < len(wordSearch[y]) {
+		// fmt.Printf("Checking %c %c %c\n", wordSearch[y][x+1], wordSearch[y][x+2], wordSearch[y][x+3])
+		if wordSearch[y][x+1] == 'M' && wordSearch[y][x+2] == 'A' && wordSearch[y][x+3] == 'S' {
+			count++
+		}
+	}
+	// check up-right
+	if y-3 >= 0 && x+3 < len(wordSearch[y]) {
+		// fmt.Printf("Checking %c %c %c\n", wordSearch[y-1][x+1], wordSearch[y-2][x+2], wordSearch[y-3][x+3])
+		if wordSearch[y-1][x+1] == 'M' && wordSearch[y-2][x+2] == 'A' && wordSearch[y-3][x+3] == 'S' {
+			count++
+		}
+	}
+	return count
+}

day4/run

@@ -0,0 +1,4 @@
+#!/bin/bash
+
+go build -o ./bin/solution ./main.go
+./bin/solution "$1"