Merge pull request prabhupant#367 from cheymonty/stack_using_list

prabhupant · web-flow · commit c685585e3e1a · 2020-06-24T21:54:47.000+05:30
Stack using list
diff --git a/data_structures/linked_list/delete_last_occurrence.py b/data_structures/linked_list/delete_last_occurrence.py
@@ -0,0 +1,32 @@
+class Node():
+
+    def __init__(self, val):
+        self.val = val
+        self.next = None
+
+def delete_last_occurrence(head, val):
+    if not head:
+        return None
+
+    curr = head
+    prev = None
+    final_prev = None
+    final_occ = None
+
+    while curr != None:
+        if curr.val == val:
+            final_prev = prev
+            final_occ = curr
+        
+        prev = curr
+        curr = curr.next
+
+    
+    if final_occ:
+        # special case that checks for a 1 node list that equals the val
+        if final_prev:
+            final_prev.next = final_occ.next
+        else:
+            head = None
+    
+    return head
diff --git a/data_structures/linked_list/index.md b/data_structures/linked_list/index.md
@@ -9,3 +9,4 @@
 * [Odd-Even Arrangement](odd_even_arrangement.py)
 * [Merge Linked List](merge_linked_list.py)
 * [Remove Duplicates](remove_duplicates.py)
+* [Delete Last Occurrence](delete_last_occurrence.py)
diff --git a/data_structures/stack/stack_using_list.py b/data_structures/stack/stack_using_list.py
@@ -0,0 +1,25 @@
+class Stack():
+    """
+    Stack follows Last-In-First-Out methodology
+    """
+
+    def __init__(self):
+        self.entries = []
+
+    def size(self):
+        return len(self.entries)
+
+    def push(self, val):
+        self.entries.append(val)
+
+    def pop(self):
+        if self.size() > 0:
+            self.entries.pop(self.size() - 1)
+
+    
+
+
+
+
+    
+    
