Flattening_a_linked_list.cpp

Author: paurush11

Data Structures/Linked Lists/Singly Linked List/Flattening_a_link_list.cpp

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+// Given a Linked List of size N, where every node represents a sub-linked-list and contains two pointers:
+// (i) a next pointer to the next node,
+// (ii) a bottom pointer to a linked list where this node is head.
+// Each of the sub-linked-list is in sorted order.
+// Flatten the Link List such that all the nodes appear in a single level while maintaining the sorted order.
+// Note: The flattened list will be printed using the bottom pointer instead of next pointer.
+
+
+
+// Example 1:
+
+// Input:
+// 5 -> 10 -> 19 -> 28
+// |     |     |     |
+// 7     20    22   35
+// |           |     |
+// 8          50    40
+// |                 |
+// 30               45
+// Output:  5-> 7-> 8- > 10 -> 19-> 20->
+// 22-> 28-> 30-> 35-> 40-> 45-> 50.
+// Explanation:
+// The resultant linked lists has every
+// node in a single level.
+// (Note: | represents the bottom pointer.)
+
+
+// Example 2:
+
+// Input:
+// 5 -> 10 -> 19 -> 28
+// |          |
+// 7          22
+// |          |
+// 8          50
+// |
+// 30
+// Output: 5->7->8->10->19->20->22->30->50
+// Explanation:
+// The resultant linked lists has every
+// node in a single level.
+
+// (Note: | represents the bottom pointer.)
+
+// Expected Time Complexity: O(N*M)
+// Expected Auxiliary Space: O(1)
+
+// Company Tags
+// Innovation Labs Amazon Drishti-Soft Flipkart Goldman Sachs Microsoft Paytm Payu Qualcomm Snapdeal Visa
+
+/* Node structure  used in the program
+
+struct Node{
+	int data;
+	struct Node * next;
+	struct Node * bottom;
+
+	Node(int x){
+	    data = x;
+	    next = NULL;
+	    bottom = NULL;
+	}
+
+};
+*/
+
+/*  Function which returns the  root of
+    the flattened linked list. */
+Node *flatten(Node *root)
+{
+    vector<int>s;
+    Node* secroot = root;
+    while(secroot){
+        Node* temp = secroot;
+        while(temp){
+            s.push_back(temp->data);
+            temp = temp->bottom;
+        }
+        secroot = secroot->next;
+    }
+    sort(s.begin(), s.end());
+    Node* root2 = new Node(0);
+    Node* dummy = root2;
+    for(auto i: s){
+        Node* n = new Node(i);
+        dummy->bottom = n;
+        dummy = dummy->bottom;
+    }
+    return root2->bottom;
+
+
+}
+