min stack solution

Author: BrianRuizy

solutions/155 - Min Stack.py

@@ -0,0 +1,54 @@
+import sys
+
+
+# implementation of queue data structure from scratch using list
+class Node:
+    def __init__(self, data=None, next=None):
+        self.data = data
+        self.next = next
+
+
+class MinStack:
+    def __init__(self):
+        self.head = None
+
+    def __repr__(self):
+        # traverse stack and print all values
+        curr = self.head
+        nodes_list = []
+        while curr:
+            nodes_list.append(str(curr.data))
+            curr = curr.next
+        nodes_list.append('None')
+        return ', '.join(nodes_list)
+
+    def pop(self):
+        # remove node from head
+        current = self.head
+        self.head = current.next
+        current = None
+
+    def push(self, x):
+        # insert new node between head and first element in the list
+        new_node = Node(data=x)  # initialize new node
+        new_node.next = self.head
+        self.head = new_node
+
+    def top(self):
+        try:
+            top = self.head.data
+        except AttributeError:
+            top = 'Stack is empty'
+        return top
+
+    def getMin(self):
+        if self.head is None:
+            return None
+
+        minimum = sys.maxsize
+        current = self.head
+        while current is not None:
+            if minimum > current.data:
+                minimum = current.data
+            current = current.next
+        return minimum