144 lines
2.9 KiB
Go
144 lines
2.9 KiB
Go
package day13
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import (
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"adventofcode2023/utils"
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"fmt"
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"strings"
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)
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type mirrorLoc struct {
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orient string
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index int
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}
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func Part1(input string) int {
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count := 0
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patterns := strings.Split(input, "\n\n")
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for p, pattern := range patterns {
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rows := strings.Split(pattern, "\n")
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if v, ok := findMirror(rows); ok {
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count = count + v * 100
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} else {
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cols := swap(rows)
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if v, ok := findMirror(cols); ok {
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count = count + v
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} else {
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utils.PanicOnErr(fmt.Errorf("p: %v\n %v\n", p, pattern))
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}
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}
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}
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return count
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}
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func Part2(input string) int {
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count := 0
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patterns := strings.Split(input, "\n\n")
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for p, pattern := range patterns {
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rows := strings.Split(pattern, "\n")
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loc, _ := findMirrorLoc(rows)
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found := false
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for i:=0;i<len(rows[0])*len(rows);i++{
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newRows := smudge(i, rows)
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if v, ok := findNewMirrorLoc(loc, newRows); ok {
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if v != loc {
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found = true
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if v.orient == "row" {
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count = count + v.index * 100
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} else {
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count = count + v.index
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}
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break
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}
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}
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}
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if ! found {
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utils.PanicOnErr(fmt.Errorf("p: %v\n %v\n", p, pattern))
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}
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}
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return count
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}
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func smudge(i int, rows []string) []string {
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out := make([]string, len(rows))
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copy(out, rows)
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col := i % len(rows[0])
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row := i / len(rows[0])
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if col >= 0 && col < len(rows[0]) {
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v := rows[row][col]
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if v == '#' {
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out[row] = out[row][:col] + "." + out[row][col+1:]
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} else {
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out[row] = out[row][:col] + "#" + out[row][col+1:]
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}
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}
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return out
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}
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func findNewMirrorLoc(loc mirrorLoc, rows []string) (mirrorLoc, bool) {
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if v, ok := findNewMirror(loc, "row", rows); ok {
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return mirrorLoc{"row", v}, true
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}
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cols := swap(rows)
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if v, ok := findNewMirror(loc, "col", cols); ok {
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return mirrorLoc{"col", v}, true
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}
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return mirrorLoc{}, false
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}
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func findMirrorLoc(rows []string) (mirrorLoc, bool) {
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if v, ok := findMirror(rows); ok {
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return mirrorLoc{"row", v}, true
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}
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cols := swap(rows)
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if v, ok := findMirror(cols); ok {
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return mirrorLoc{"col", v}, true
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}
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return mirrorLoc{}, false
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}
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func swap(in []string) []string {
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out := []string{}
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for j:=0;j<len(in[0]);j++ {
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o := ""
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for i:=0;i<len(in);i++ {
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o = o + string(in[i][j])
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}
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out = append(out, o)
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}
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return out
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}
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func findMirror(rows []string) (int, bool) {
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for i:=0;i<len(rows)-1;i++ {
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if rows[i] == rows[i+1] {
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if isMirror(i, 0, rows) {
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return i+1, true
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}
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}
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}
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return -1, false
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}
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func findNewMirror(loc mirrorLoc, orient string, rows []string) (int, bool) {
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for i:=0;i<len(rows)-1;i++ {
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if orient == loc.orient && i == loc.index - 1{ continue }
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if rows[i] == rows[i+1] {
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if isMirror(i, 0, rows) {
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return i+1, true
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}
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}
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}
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return -1, false
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}
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func isMirror(i int, offset int, rows []string) bool {
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if i == 0 || i == len(rows) - 1 { return true }
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if i - offset < 0 || i+1+offset > len(rows) - 1 { return true }
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if rows[i+1+offset] == rows[i-offset] {
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return isMirror(i, offset+1, rows)
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}
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return false
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} |