add 669

Author: fishercoder1534

README.md

@@ -23,6 +23,7 @@ Your ideas/fixes/algorithms are more than welcome!
 |  #  |      Title     |   Solutions   | Time          | Space         | Difficulty  | Tag          | Notes
 |-----|----------------|---------------|---------------|---------------|-------------|--------------|-----
 |671|[Second Minimum Node In a Binary Tree](https://leetcode.com/problems/second-minimum-node-in-a-binary-tree/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_671.java) | O(n) | O(n) | Easy | Tree, DFS
+|669|[Trim a Binary Search Tree](https://leetcode.com/problems/trim-a-binary-search-tree/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_669.java) | O(n) | O(1) | Easy | Tree, DFS
 |668|[Kth Smallest Number in Multiplication Table](https://leetcode.com/problems/kth-smallest-number-in-multiplication-table/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_668.java) | O(logm*n) | O(1) | Hard | Binary Search
 |667|[Beautiful Arrangement II](https://leetcode.com/problems/beautiful-arrangement-ii/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_667.java) | O(n) | O(1) | Medium | Array
 |666|[Path Sum IV](https://leetcode.com/problems/path-sum-iv/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_666.java) | O(1) | O(1) | Medium | Tree, DFS

src/main/java/com/fishercoder/solutions/_669.java

@@ -0,0 +1,69 @@
+package com.fishercoder.solutions;
+
+import com.fishercoder.common.classes.TreeNode;
+
+/**
+ * 669. Trim a Binary Search Tree
+ *
+ * Given a binary search tree and the lowest and highest boundaries as L and R,
+ * trim the tree so that all its elements lies in [L, R] (R >= L).
+ * You might need to change the root of the tree, so the result should return the new root of the trimmed binary search tree.
+
+ Example 1:
+
+ Input:
+   1
+  / \
+ 0   2
+
+ L = 1
+ R = 2
+
+ Output:
+ 1
+  \
+  2
+
+ Example 2:
+
+ Input:
+  3
+ / \
+0   4
+ \
+ 2
+ /
+1
+
+ L = 1
+ R = 3
+
+ Output:
+    3
+   /
+  2
+ /
+1
+
+ */
+public class _669 {
+    public static class Solution1 {
+        public TreeNode trimBST(TreeNode root, int L, int R) {
+            if (root == null) {
+                return root;
+            }
+
+            if (root.val > R) {
+                return trimBST(root.left, L, R);
+            }
+
+            if (root.val < L) {
+                return trimBST(root.right, L, R);
+            }
+
+            root.left = trimBST(root.left, L, R);
+            root.right = trimBST(root.right, L, R);
+            return root;
+        }
+    }
+}

src/test/java/com/fishercoder/_669Test.java

@@ -0,0 +1,37 @@
+package com.fishercoder;
+
+import com.fishercoder.common.classes.TreeNode;
+import com.fishercoder.common.utils.TreeUtils;
+import com.fishercoder.solutions._669;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+import java.util.Arrays;
+
+import static org.junit.Assert.assertEquals;
+
+public class _669Test {
+    private static _669.Solution1 solution1;
+    private static TreeNode root;
+    private static TreeNode expected;
+
+    @BeforeClass
+    public static void setup() {
+        solution1 = new _669.Solution1();
+    }
+
+    @Test
+    public void test1() {
+        root = TreeUtils.constructBinaryTree(Arrays.asList(1, 0, 2));
+        expected = TreeUtils.constructBinaryTree(Arrays.asList(1, null, 2));
+        assertEquals(expected, solution1.trimBST(root, 1, 2));
+    }
+
+    @Test
+    public void test2() {
+        root = TreeUtils.constructBinaryTree(Arrays.asList(3, 0, 4, null, 2, null, null, 1));
+        expected = TreeUtils.constructBinaryTree(Arrays.asList(3, 2, null, 1));
+        assertEquals(expected, solution1.trimBST(root, 1, 3));
+    }
+
+}