add day 6 with part 2 being incomplete

day6/distinct_positions.go

@@ -0,0 +1,125 @@
+package main
+
+import (
+    "os"
+    "fmt"
+    "strings"
+)
+
+// type definitions
+type Direction int
+const (
+	Up Direction = iota + 1
+	Down
+	Left
+	Right
+)
+
+type state struct {
+    field [][]rune
+    guard_x int
+    guard_y int
+    direction Direction
+}
+
+func new_state(text string) *state {
+    lines := strings.Split(text, "\n")
+    field := make([][]rune, len(lines))
+    guard := [2]int{-1,-1}
+
+    for y := range lines {
+        field[y] = []rune(lines[y])
+
+        for x, r := range field[y] {
+            if r == '^' {
+                guard = [2]int{x, y}
+                field[y][x] = '.'
+            }
+        }
+    }
+
+    s := state{field: field, guard_x: guard[0], guard_y: guard[1], direction: Up}
+    return &s
+}
+
+// general util
+func check(e error) {
+    if e != nil { panic(e) }
+}
+
+func add_non_duplicate(slice [][2]int, elem [2]int) [][2]int {
+    for _, e := range slice {
+        if e == elem { return slice }
+    }
+    return append(slice, elem)
+}
+
+
+// simulation functions
+func iter(s *state) *state {
+    new_guard_x := s.guard_x
+    new_guard_y := s.guard_y
+    
+    // try to move
+    switch {
+        case s.direction == Up:
+            new_guard_y--
+        case s.direction == Down:
+            new_guard_y++
+        case s.direction == Left:
+            new_guard_x--
+        case s.direction == Right:
+            new_guard_x++
+    }
+    
+    // if guard is outside of the field
+    if new_guard_x < 0 || new_guard_y < 0 || new_guard_x >= len(s.field[0]) || new_guard_y >= len(s.field) {
+        new_guard_x = -1
+        new_guard_y = -1
+    } else if s.field[new_guard_y][new_guard_x] == '#' {
+    // correct if path is blocked
+        switch {
+            case s.direction == Up:
+                new_guard_y++
+                s.direction = Right
+                new_guard_x++
+            case s.direction == Down:
+                new_guard_y--
+                s.direction = Left
+                new_guard_x--
+            case s.direction == Left:
+                new_guard_x++
+                s.direction = Up
+                new_guard_y--
+            case s.direction == Right:
+                new_guard_x--
+                s.direction = Down
+                new_guard_y++
+        }
+    }
+
+    // set new guard coordinates
+    s.guard_x = new_guard_x
+    s.guard_y = new_guard_y
+
+    return s
+}
+
+// main loop
+func main() {
+
+    // read in file
+    dat, err := os.ReadFile("data.txt")
+    check(err)
+    dat_str := string(dat[:len(dat) - 1])
+    
+    stateobj := new_state(dat_str)
+
+    distinct_pos := make([][2]int, 0)
+    for stateobj.guard_x >= 0 {
+        distinct_pos = add_non_duplicate(distinct_pos, [2]int{stateobj.guard_x, stateobj.guard_y})
+        stateobj = iter(stateobj)
+    }
+
+    fmt.Println(len(distinct_pos))
+}