Add BfsTest

src/test/java/BfsTest.java

@@ -0,0 +1,65 @@
+import org.junit.jupiter.api.Test;
+
+import java.util.LinkedList;
+import java.util.Queue;
+
+// - https://leetcode.com/problems/number-of-islands/
+public class BfsTest {
+    private char[][] grid;
+
+    @Test
+    void numIslands() {
+        char[][] grid = {
+                {'1', '1', '0', '0', '0'},
+                {'1', '1', '0', '0', '0'},
+                {'0', '0', '1', '0', '0'},
+                {'0', '0', '0', '1', '1'},
+        };
+//        char[][] grid = {
+//                {'1', '1', '1', '1', '0'},
+//                {'1', '1', '0', '1', '0'},
+//                {'1', '1', '0', '0', '0'},
+//                {'0', '0', '0', '0', '0'}};
+        int output = 1;
+        int numOfLands = 0;
+        this.grid = grid;
+        for (int i = 0; i < grid.length; i++) {
+            for (int j = 0; j < grid[0].length; j++) {
+                if (grid[i][j] == '1') {
+                    numOfLands++;
+                    bfs(i, j);
+                }
+            }
+        }
+        System.out.println("numOfLands = " + numOfLands);
+    }
+
+    private void bfs(int i, int j) {
+        Queue<Integer> que = new LinkedList<>();
+        que.add(i);
+        que.add(j);
+        grid[i][j] = '0';
+
+        int[] yDir = {0, -1, 0, 1};
+        int[] xDir = {1, 0, -1, 0};
+
+        while (!que.isEmpty()) {
+            int y = que.poll();
+            int x = que.poll();
+
+            for (int d = 0; d < 4; d++) {
+                int ny = y + yDir[d];
+                int nx = x + xDir[d];
+
+                if (ny < 0 || ny >= grid.length || nx < 0 || nx >= grid[0].length) {
+                    continue;
+                }
+                if (grid[ny][nx] == '1') {
+                    que.add(ny);
+                    que.add(nx);
+                    grid[ny][nx] = '0';
+                }
+            }
+        }
+    }
+}