Add Leetcode 270. Closest Binary Search Tree Value

src/leetcode/LC_270/Solution270.java

@@ -0,0 +1,35 @@
+package leetcode.LC_270;
+
+import base.TreeNode;
+
+/**
+ * 270. Closest Binary Search Tree Value
+ */
+class Solution270 {
+    Integer candidate = null;
+    Double minDiff = null;
+
+    public int closestValue(TreeNode root, double target) {
+        recur(root, target);
+        return candidate;
+    }
+
+    private void recur(TreeNode node, final double target) {
+        if (node == null)
+            return;
+
+        // Update candidate if diff smaller than minDiff
+        double absDiff = Math.abs(node.val - target);
+        if (minDiff == null || absDiff < minDiff) {
+            candidate = node.val;
+            minDiff = absDiff;
+        }
+
+        // Recursion w/ pruning
+        if (target > node.val) {
+            recur(node.right, target);
+        } else  {
+            recur(node.left, target);
+        }
+    }
+}

src/leetcode/LC_270/Solution270Test.java

@@ -0,0 +1,27 @@
+package leetcode.LC_270;
+
+import base.TreeNode;
+import org.junit.Test;
+
+import static org.junit.Assert.*;
+
+public class Solution270Test {
+
+    @Test
+    public void closestValue_0() {
+        TreeNode n1 = new TreeNode(0);
+        assertEquals(0, new Solution270().closestValue(n1, 2147483648.0));
+    }
+
+    @Test
+    public void closestValue_1() {
+        TreeNode n31 = new TreeNode(1);
+        TreeNode n32 = new TreeNode(3);
+        TreeNode n21 = new TreeNode(2);
+        TreeNode n22 = new TreeNode(5);
+        n21.left = n31; n21.right = n32;
+        TreeNode n1 = new TreeNode(4);
+        n1.left = n21; n1.right = n22;
+        assertEquals(4, new Solution270().closestValue(n1, 3.714286));
+    }
+}