add solver for part b

Advent of Code/2024/Day 06/solver.go

@@ -9,12 +9,13 @@ import (
 )
 
 var puzzle_file_name = "puzzle_input.txt"
-var level [][] string
-var guard_pos struct {
+type level [][] string
+type guard_info struct {
     col int
     row int
     direction int
 }
+var infinite_loop_count = 0
 
 //              { -1, 0 }
 //  { 0, -1}                { 0, +1 }
@@ -26,14 +27,13 @@ var directions = [][]int {
     {0, -1},
 }
 
-func load_puzzle_from_file(target_file_name string){
-    file, err := os.Open(target_file_name)
-    if err != nil{
-        return
-    }
+func load_puzzle_from_file(target_file_name string) (level, guard_info){
+    file, _ := os.Open(target_file_name)
     defer file.Close()
 
     scanner := bufio.NewScanner(file)
+    var new_level level
+    var new_guard guard_info
 
     line_counter := 0
     for scanner.Scan(){
@@ -47,9 +47,9 @@ func load_puzzle_from_file(target_file_name string){
             }
 
             if stringified == "^"{
-                guard_pos.col = idx
-                guard_pos.row = line_counter
-                guard_pos.direction = 0
+                new_guard.col = idx
+                new_guard.row = line_counter
+                new_guard.direction = 0
                 line_array = append(line_array, stringified)
             }
 
@@ -57,72 +57,79 @@ func load_puzzle_from_file(target_file_name string){
                 line_array = append(line_array, stringified)
             }
         }
-        level = append(level, line_array)
+        new_level = append(new_level, line_array)
         line_counter++ 
     }
+    return new_level, new_guard
 }
 
 
-func solve_movement(){
-    fmt.Println("Map Size: ", len(level) -1, len(level[0]) -1)
-    fmt.Println("Guard Starting Position: ", guard_pos.row, guard_pos.col, guard_pos.direction)
-
+func solve_movement(test_level level, test_guard guard_info) (int){
     // create an indetic sized map to track places that were visited
     var visited [][]int 
-    for range level{
+    for range test_level{
         var row []int
-        for range level[0] {
+        for range test_level[0] {
             row = append(row, 0)
         }
         visited = append(visited, row)
     }
 
     // mark starting position as visited
-    visited[guard_pos.row][guard_pos.col] = 1
+    visited[test_guard.row][test_guard.col] = 1
     left_map := false
+    max_visits_assume_infinite_loop := 10
+    max_visits_seen := 0
 
     for {
         if left_map {
             break
         }
 
-        next_row := guard_pos.row + directions[guard_pos.direction][0]
-        next_col := guard_pos.col + directions[guard_pos.direction][1]
+        next_row := test_guard.row + directions[test_guard.direction][0]
+        next_col := test_guard.col + directions[test_guard.direction][1]
         // check for out of bounds
         is_row_negative := next_row < 0
         is_col_negative := next_col < 0
-        is_row_oob := next_row > (len(level) -1)
-        is_col_oob := next_col > (len(level[0]) -1)
+        is_row_oob := next_row > (len(test_level) -1)
+        is_col_oob := next_col > (len(test_level[0]) -1)
         if is_col_negative || is_row_negative || is_row_oob || is_col_oob {
             left_map = true
             continue
         }
 
-        if level[next_row][next_col] == "#"{
-            guard_pos.direction++
-            if guard_pos.direction > len(directions) -1 {
-                guard_pos.direction = 0
+        if test_level[next_row][next_col] == "#"{
+            test_guard.direction++
+            if test_guard.direction > len(directions) -1 {
+                test_guard.direction = 0
             }
         }
 
-        if level[next_row][next_col] != "#" {
-            guard_pos.row = next_row
-            guard_pos.col = next_col
-            visited[next_row][next_col] = 1
+        if test_level[next_row][next_col] != "#" {
+            test_guard.row = next_row
+            test_guard.col = next_col
+            visited[next_row][next_col]++
+            if visited[next_row][next_col] > max_visits_seen{
+                max_visits_seen++
+            }
         }
 
-        
+        if max_visits_seen > max_visits_assume_infinite_loop {
+            infinite_loop_count++
+            break
+        }
     }
 
     places_visited := 0 
     for row := range visited{
         for col := range visited[row]{
-            if visited[row][col] == 1 {
+            if visited[row][col] >= 1 {
                 places_visited++
             }
         }
     }
-    fmt.Println("Visited Places: ", places_visited)
+
+    return places_visited
 }
 
 func time_track(start time.Time, name string){
@@ -130,9 +137,39 @@ func time_track(start time.Time, name string){
     log.Printf("%s took %s", name, elapsed)
 }
 
+func clone_level(origin level)(level){
+    new_level := make(level, len(origin))
+    for i := range origin{
+        new_level[i] = make([]string, len(origin[i]))
+        copy(new_level[i], origin[i])
+    }
+    return new_level
+}
+
+func test_for_infinite_loop(base_level level, test_guard guard_info){
+    for row := range base_level {
+        for col := range base_level[row] {
+            if test_guard.row == row && test_guard.col == col {
+                continue
+            }
+
+            if base_level[row][col] == "#"{
+                continue
+            }
+
+            isolated_level := clone_level(base_level)
+            isolated_level[row][col] = "#"
+
+            solve_movement(isolated_level, test_guard)
+        }
+    }
+    fmt.Println("Total Infinite Loops Found: ", infinite_loop_count)
+}
 
 func main(){
     defer time_track(time.Now(), "main")
-    load_puzzle_from_file(puzzle_file_name)
-    solve_movement()
+    level, guard := load_puzzle_from_file(puzzle_file_name)
+    places_visited := solve_movement(level, guard)
+    fmt.Println("Total Places Visited: ", places_visited)
+    test_for_infinite_loop(level, guard)
 }