Added solution to create minimal bst with sorted array input

YogenRaii · YogenRaii · commit d0e4aba4cfc2 · 2019-06-02T15:28:30.000-05:00
diff --git a/src/main/java/com/eprogrammerz/examples/algorithm/trees/MinimalBST.java b/src/main/java/com/eprogrammerz/examples/algorithm/trees/MinimalBST.java
@@ -0,0 +1,49 @@
+package com.eprogrammerz.examples.algorithm.trees;
+
+import org.junit.Test;
+
+import java.util.Arrays;
+import java.util.List;
+
+import static org.junit.Assert.assertEquals;
+
+public class MinimalBST {
+    public Node constructMinBST(List<Integer> vals) {
+        if (vals == null || vals.isEmpty()) return null;
+
+        return constructMinBST(vals, 0, vals.size() - 1);
+    }
+
+    public Node constructMinBST(List<Integer> vals, int start, int end) {
+        if (start > end) return null;
+
+        int mid = (end - start) / 2 + start;
+
+        Node node = new Node(vals.get(mid));
+
+        node.left = constructMinBST(vals, start, mid - 1);
+        node.right = constructMinBST(vals, mid + 1, end);
+
+        return node;
+    }
+
+    @Test
+    public void testConstructMinimalTree() {
+        List<Integer> vals = Arrays.asList(1, 2, 3, 4, 5, 6, 7);
+
+        /**
+         *              4
+         *             /  \
+         *           2      6
+         *         /   \   /  \
+         *        1    3   5   7
+         */
+        Node tree = constructMinBST(vals);
+        assertEquals(3, maxDepth(tree));
+    }
+
+    public int maxDepth(Node tree) {
+        if (tree == null) return 0;
+        return Math.max(maxDepth(tree.left), maxDepth(tree.right)) + 1;
+    }
+}
