forest fire

src/Fire.java

@@ -1,3 +1,6 @@
+import java.util.LinkedList;
+import java.util.Queue;
+
 public class Fire {
     /**
      * Returns how long it takes for all vulnerable trees to be set on fire if a
@@ -38,6 +41,54 @@ public class Fire {
     public static int timeToBurn(char[][] forest, int matchR, int matchC) {
         // HINT: when adding to your BFS queue, you can include more information than
         // just a location. What other information might be useful?
-        return -1;
+
+
+
+        int rows = forest.length;
+        int cols = forest[0].length;
+
+        boolean[][] visited = new boolean[rows][cols];
+
+        // Check that starting point is a tree
+        if (forest[matchR][matchC] != 't') {
+            return -1;
+        }
+
+        int[][] directions = {
+            {-1, 0},  // up
+            {1, 0},   // down
+            {0, -1},  // left
+            {0, 1}    // right
+        };
+
+        Queue<int[]> queue = new LinkedList<>();
+        queue.add(new int[]{matchR, matchC, 0});
+        visited[matchR][matchC] = true;
+
+        int maxTime = 0;
+
+        while (!queue.isEmpty()) {
+            int[] current = queue.poll();
+            int r = current[0];
+            int c = current[1];
+            int time = current[2];
+
+            maxTime = Math.max(maxTime, time);
+
+            for (int[] dir : directions) {
+                int newR = r + dir[0];
+                int newC = c + dir[1];
+
+                if (newR >= 0 && newR < rows && newC >= 0 && newC < cols
+                        && !visited[newR][newC]
+                        && forest[newR][newC] == 't') {
+
+                    visited[newR][newC] = true;
+                    queue.add(new int[]{newR, newC, time + 1});
+                }
+            }
+        }
+
+        return maxTime;
     }
 }

src/FireTest.java

@@ -20,4 +20,58 @@ public void testTimeToBurnExample() {
 
         assertEquals(expected, actual);
     }
+
+    @Test
+    public void testSingleTree() {
+        char[][] forest = {
+            {'t'}
+        };
+        assertEquals(0, Fire.timeToBurn(forest, 0, 0));
+    }
+
+    @Test
+    public void testSingleEmptySpace() {
+        char[][] forest = {
+            {'.'}
+        };
+        assertEquals(-1, Fire.timeToBurn(forest, 0, 0));
+    }
+
+    @Test
+    public void testDisconnectedTrees() {
+        char[][] forest = {
+            {'t', '.', 't'},
+            {'.', '.', '.'},
+            {'t', '.', 't'}
+        };
+        assertEquals(0, Fire.timeToBurn(forest, 0, 0));
+    }
+
+    @Test
+    public void testFullBlockOfTrees() {
+        char[][] forest = {
+            {'t', 't'},
+            {'t', 't'}
+        };
+        assertEquals(2, Fire.timeToBurn(forest, 0, 0));
+    }
+
+    @Test
+    public void testFireStartsOnGround() {
+        char[][] forest = {
+            {'t', 't'},
+            {'.', 't'}
+        };
+        assertEquals(-1, Fire.timeToBurn(forest, 1, 0));
+    }
+
+    @Test
+    public void testEdgeSpread() {
+        char[][] forest = {
+            {'t', 't', 't', '.', '.'},
+            {'.', '.', 't', '.', '.'},
+            {'.', '.', 't', 't', 't'}
+        };
+        assertEquals(6, Fire.timeToBurn(forest, 0, 0));
+    }
 }