86 lines
1.8 KiB
Go
86 lines
1.8 KiB
Go
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package main
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import (
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"fmt"
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h "git.bullercodeworks.com/brian/adventofcode/helpers"
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)
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func main() {
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inp := h.StdinToCoordMap()
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part1(inp)
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part2(inp)
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}
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func part1(m h.CoordByteMap) {
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var total int
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for y := m.TLY; y <= m.BRY; y++ {
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for x := m.TLX; x <= m.BRX; x++ {
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total += checkPos(m, h.Coordinate{X: x, Y: y})
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}
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}
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fmt.Println("# Part 1")
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fmt.Println("Instances of XMAS:", total)
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}
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func part2(m h.CoordByteMap) {
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var total int
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for y := m.TLY; y <= m.BRY; y++ {
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for x := m.TLX; x <= m.BRX; x++ {
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if checkXPos(m, h.Coordinate{X: x, Y: y}) {
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total++
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}
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}
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}
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fmt.Println("# Part 2")
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fmt.Println("Instances of X-MAS:", total)
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}
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// checkPos takes an x,y and returns how many instances of
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// 'XMAS' occur starting there.
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func checkPos(m h.CoordByteMap, c h.Coordinate) int {
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if m.Get(c) != 'X' {
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return 0
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}
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var total int
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for _, dir := range []h.Coordinate{
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{X: -1, Y: 0}, // North
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{X: -1, Y: 1}, // Northeast
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{X: 0, Y: 1}, // East
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{X: 1, Y: 1}, // Southeast
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{X: 1, Y: 0}, // South
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{X: 1, Y: -1}, // Southwest
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{X: 0, Y: -1}, // West
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{X: -1, Y: -1}, // Northwest
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} {
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if checkDir(m, c, dir, []byte{'X', 'M', 'A', 'S'}) {
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total++
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}
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}
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return total
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}
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// checkDir follows a direction to look for the word returning true if found.
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func checkDir(m h.CoordByteMap, c h.Coordinate, dir h.Coordinate, word []byte) bool {
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if len(word) == 0 {
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return true
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}
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if m.Get(c) != word[0] {
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return false
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}
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return checkDir(m, c.Relative(dir), dir, word[1:])
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}
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func checkXPos(m h.CoordByteMap, c h.Coordinate) bool {
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if m.Get(c) != 'A' {
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return false
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}
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// A X-Mas can be:
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// M S S M M M S S
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// A A A A
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// M S S M S S M M
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wrk := string([]byte{m.Get(c.NE()), m.Get(c.SW()), m.Get(c.NW()), m.Get(c.SE())})
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return wrk == "MSMS" || wrk == "SMSM" || wrk == "MSSM" || wrk == "SMMS"
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}
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