diff --git a/src/main/java/g0101_0200/s0198_house_robber/Solution.java b/src/main/java/g0101_0200/s0198_house_robber/Solution.java
new file mode 100644
index 000000000..b325a971b
--- /dev/null
+++ b/src/main/java/g0101_0200/s0198_house_robber/Solution.java
@@ -0,0 +1,22 @@
+package g0101_0200.s0198_house_robber;
+
+public class Solution {
+    public int rob(int[] nums) {
+        if (nums.length == 0) {
+            return 0;
+        }
+        if (nums.length == 1) {
+            return nums[0];
+        }
+        if (nums.length == 2) {
+            return Math.max(nums[0], nums[1]);
+        }
+        int[] profit = new int[nums.length];
+        profit[0] = nums[0];
+        profit[1] = Math.max(nums[1], nums[0]);
+        for (int i = 2; i < nums.length; i++) {
+            profit[i] = Math.max(profit[i - 1], nums[i] + profit[i - 2]);
+        }
+        return profit[nums.length - 1];
+    }
+}
diff --git a/src/main/java/g0101_0200/s0199_binary_tree_right_side_view/Solution.java b/src/main/java/g0101_0200/s0199_binary_tree_right_side_view/Solution.java
new file mode 100644
index 000000000..254f99bb4
--- /dev/null
+++ b/src/main/java/g0101_0200/s0199_binary_tree_right_side_view/Solution.java
@@ -0,0 +1,38 @@
+package g0101_0200.s0199_binary_tree_right_side_view;
+
+import com_github_leetcode.TreeNode;
+import java.util.ArrayList;
+import java.util.List;
+
+/*
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public List<Integer> rightSideView(TreeNode root) {
+        List<Integer> list = new ArrayList<>();
+        recurse(root, 0, list);
+        return list;
+    }
+
+    private void recurse(TreeNode node, int level, List<Integer> list) {
+        if (node != null) {
+            if (list.size() < level + 1) {
+                list.add(node.val);
+            }
+            recurse(node.right, level + 1, list);
+            recurse(node.left, level + 1, list);
+        }
+    }
+}
diff --git a/src/main/java/g0101_0200/s0200_number_of_islands/Solution.java b/src/main/java/g0101_0200/s0200_number_of_islands/Solution.java
new file mode 100644
index 000000000..7ffbde2b8
--- /dev/null
+++ b/src/main/java/g0101_0200/s0200_number_of_islands/Solution.java
@@ -0,0 +1,29 @@
+package g0101_0200.s0200_number_of_islands;
+
+public class Solution {
+    public int numIslands(char[][] grid) {
+        int islands = 0;
+        if (grid != null && grid.length != 0 && grid[0].length != 0) {
+            for (int i = 0; i < grid.length; i++) {
+                for (int j = 0; j < grid[0].length; j++) {
+                    if (grid[i][j] == '1') {
+                        dfs(grid, i, j);
+                        islands++;
+                    }
+                }
+            }
+        }
+        return islands;
+    }
+
+    private void dfs(char[][] grid, int x, int y) {
+        if (x < 0 || grid.length <= x || y < 0 || grid[0].length <= y || grid[x][y] != '1') {
+            return;
+        }
+        grid[x][y] = 'x';
+        dfs(grid, x + 1, y);
+        dfs(grid, x - 1, y);
+        dfs(grid, x, y + 1);
+        dfs(grid, x, y - 1);
+    }
+}
diff --git a/src/test/java/g0101_0200/s0198_house_robber/SolutionTest.java b/src/test/java/g0101_0200/s0198_house_robber/SolutionTest.java
new file mode 100644
index 000000000..7ebac8792
--- /dev/null
+++ b/src/test/java/g0101_0200/s0198_house_robber/SolutionTest.java
@@ -0,0 +1,18 @@
+package g0101_0200.s0198_house_robber;
+
+import static org.hamcrest.CoreMatchers.equalTo;
+import static org.hamcrest.MatcherAssert.assertThat;
+
+import org.junit.Test;
+
+public class SolutionTest {
+    @Test
+    public void rob() {
+        assertThat(new Solution().rob(new int[] {1, 2, 3, 1}), equalTo(4));
+    }
+
+    @Test
+    public void rob2() {
+        assertThat(new Solution().rob(new int[] {2, 7, 9, 3, 1}), equalTo(12));
+    }
+}
diff --git a/src/test/java/g0101_0200/s0199_binary_tree_right_side_view/SolutionTest.java b/src/test/java/g0101_0200/s0199_binary_tree_right_side_view/SolutionTest.java
new file mode 100644
index 000000000..4740bf27e
--- /dev/null
+++ b/src/test/java/g0101_0200/s0199_binary_tree_right_side_view/SolutionTest.java
@@ -0,0 +1,24 @@
+package g0101_0200.s0199_binary_tree_right_side_view;
+
+import static org.hamcrest.CoreMatchers.equalTo;
+import static org.hamcrest.MatcherAssert.assertThat;
+
+import com_github_leetcode.TreeNode;
+import java.util.Arrays;
+import org.junit.Test;
+
+public class SolutionTest {
+    @Test
+    public void rightSideView() {
+        TreeNode left = new TreeNode(2, null, new TreeNode(5));
+        TreeNode right = new TreeNode(3, null, new TreeNode(4));
+        TreeNode root = new TreeNode(1, left, right);
+        assertThat(new Solution().rightSideView(root), equalTo(Arrays.asList(1, 3, 4)));
+    }
+
+    @Test
+    public void rightSideView2() {
+        TreeNode root = new TreeNode(1, null, new TreeNode(3));
+        assertThat(new Solution().rightSideView(root), equalTo(Arrays.asList(1, 3)));
+    }
+}
diff --git a/src/test/java/g0101_0200/s0200_number_of_islands/SolutionTest.java b/src/test/java/g0101_0200/s0200_number_of_islands/SolutionTest.java
new file mode 100644
index 000000000..5b14a2c58
--- /dev/null
+++ b/src/test/java/g0101_0200/s0200_number_of_islands/SolutionTest.java
@@ -0,0 +1,35 @@
+package g0101_0200.s0200_number_of_islands;
+
+import static org.hamcrest.CoreMatchers.equalTo;
+import static org.hamcrest.MatcherAssert.assertThat;
+
+import org.junit.Test;
+
+public class SolutionTest {
+    @Test
+    public void numIslands() {
+        assertThat(
+                new Solution()
+                        .numIslands(
+                                new char[][] {
+                                    {'1', '1', '1', '1', '0'},
+                                    {'1', '1', '0', '1', '0'},
+                                    {'1', '1', '0', '0', '0'},
+                                    {'0', '0', '0', '0', '0'}
+                                }),
+                equalTo(1));
+    }
+
+    public void numIslands2() {
+        assertThat(
+                new Solution()
+                        .numIslands(
+                                new char[][] {
+                                    {'1', '1', '0', '0', '0'},
+                                    {'1', '1', '0', '0', '0'},
+                                    {'0', '0', '1', '0', '0'},
+                                    {'0', '0', '0', '1', '1'}
+                                }),
+                equalTo(3));
+    }
+}