BST PR

isBST.cpp

@@ -0,0 +1,58 @@
+bool isBst(Node* root)
+{
+    if(root == NULL)
+    {
+        return true;
+    }
+
+    if(root->right!=NULL && minimum(root->right) < root->data)
+    {
+        return false;
+    }
+    if(root->left!=NULL && maximum(root->left) > root->data)
+    {
+        return false;
+    }
+
+    bool lr = isBst(root->left);
+    bool rr = isBst(root->right);
+    if(!lr || !rr)
+    {
+        return false;
+    }
+    return true;
+}
+
+
+//-------------------------------------------------------------------------------------------
+
+
+class BSTPair{
+    public:
+    int min;
+    int max;
+    bool isBST;
+};
+
+BSTPair* isBst(Node* root)
+{
+    if(root == NULL)
+    {
+        BSTPair* bp = new BSTPair();
+        bp->min = INT_MAX;
+        bp->max = INT_MIN;
+        bp->isBST = true;
+        return bp;
+    }
+
+    BSTPair* lp = isBst(root->left);
+    BSTPair* rp = isBst(root->right);
+    BSTPair* mp = new BSTPair();
+
+    mp->min = min(root->data, min(lp->min, rp->min));
+    mp->max = max(root->data, max(lp->max, rp->max));
+
+    mp->isBST = lp->isBST && rp->isBST && root->data > lp->max && root->data < rp->min;
+
+    return mp;
+}