Added lowest common ancestor

Author: FreeTymeKiyan

Other/LowestCommonAncestor.java

@@ -0,0 +1,42 @@
+/**
+ * Given a binary tree (not a binary search tree) and two values say n1 and n2, 
+ * write a program to find the least common ancestor.
+ * Allow a node to be a descendant of itself
+ * 
+ * Tags: Tree
+ */
+class LowestCommonAncestor {
+    public static void main(String[] args) {
+        
+    }
+    
+    /**
+     * If root is null, just return null
+     * If root's value matches with n1 or n2, return root
+     * If not, find lca recursively in both left and right subtrees
+     * If both are not null, one value in left and the other in right, 
+     * return root
+     * If one is not null, return that one
+     */
+    public Node findLca(Node root, int n1, int n2) {
+        if (root == null) return null;
+        if (root.val == n1 || root.val == n2) return root;
+        
+        Node leftLca = findLca(root.left, n1, n2);
+        Node rightLca = findLca(root.right, n1, n2);
+        if (leftLca != null && rightLca != null) return root;
+        return leftLca != null ? leftLca : rightLca;
+    }
+    
+    class Node {
+        int val;
+        Node left;
+        Node right;
+        
+        public Node() {}
+            
+        public Node(int v) {
+            val = v;
+        }
+    }
+}