Binary search tree least common ancestor

src/algorithm_practice/Binary_Search_Tree_Algorithms/lowestCommonAncestor/bst_lca.java

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+
+/**
+ * Created by divyam on 13/10/16.
+ * So we will first introduce the problem of least common ancestor of 2 nodes in a binary search tree
+ * <p>
+ * Let T be a rooted tree. The lowest common ancestor between two nodes n1 and n2 is defined as the lowest node in T
+ * that has both n1 and n2 as descendants (where we allow a node to be a descendant of itself)
+ * for every pair of nodes in a tree we have root node as an ancestor but the problem is to find the lowest common ancestor
+ * ie we have to find the lca_node such that the sum of distance of  the lca_node to the given nodes n1 and n2 is minimum
+ */
+
+public class bst_lca {
+    class Node {
+        int data;
+        Node left, right;
+
+        Node(int item) {
+            data = item;
+            left = right = null;
+        }
+    }
+
+    Node root;
+
+    /* Function to find LCA of n1 and n2. The function assumes that both
+       n1 and n2 are present in BST */
+    Node lca(Node node, int n1, int n2) {
+        if (node == null)
+            return null;
+
+        // If both n1 and n2 are smaller than root, then LCA lies in left
+        if (node.data > n1 && node.data > n2)
+            return lca(node.left, n1, n2);
+
+        // If both n1 and n2 are greater than root, then LCA lies in right
+        if (node.data < n1 && node.data < n2)
+            return lca(node.right, n1, n2);
+
+        //the final case when nodes n1 and n2 lie on opposite sides of the present node , we return that node
+        return node;
+    }
+
+}