DLL Delete Head-Tail (#34)

Data-Structures/Linear-Data-Structures/Linked-List/Doubly-Linked-List/02-delete-head-tail.md

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+## Delete head and tail of a DLL
+
+### Algorithm :
+
+**Delete Head :**
+
+1. If DLL is empty or is a singleton, return NULL.
+2. Else, make a `prev` pointer and point to head to keep a trck of head.
+3. Move the current head pointer to the next node.
+4. Point new head's back to NULL and prev's next to NULL to disconnect the first node.
+5. Free up the memory by deleting the prev node.
+6. Return new head.
+
+**Delete tail :**
+
+1. If DLL is empty or is a singleton, return NULL.
+2. Else, create a temporary tail pointer and point it to head.
+3. Start traversing the DLL unless we reach the actual tail node.
+4. Tail's previous node becomes our new tail by pointing actual tail's back to the previous node. This will help us to track the new tail node.
+5. Now point actual tail's back and new tail's next to NULL so it gets disconnected from the DLL.
+6. Free up the memory by deleting the actual tree.
+7. Return head.
+
+---
+
+```cpp
+Node* deleteHeadDLL(Node* head){
+    if (head == NULL || head->next == NULL){
+        return NULL;
+    }
+
+    Node* prev = head;
+    head = head->next;
+    head->back = NULL;
+    prev->next = NULL;
+
+    delete prev;
+    return head;
+}
+
+Node* deleteHeadDLL(Node* head){
+    if (head == NULL || head->next == NULL){
+        return NULL;
+    }
+    Node* tail = head;
+    while(tail->next != NULL){
+        tail = tail->next;
+    }
+    Node* newTail = tail->back;
+    tail->back = NULL:
+    newTail->next = NULL;
+
+    delete tail
+    return head;
+}
+```