master > master: code - stacks + queues data structures überarbeitet

code/python/src/data_structures/queues.py

@@ -0,0 +1,52 @@
+#!/usr/bin/env python3
+# -*- coding: utf-8 -*-
+
+# ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+# IMPORTS
+# ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+from local.typing import *;
+
+# ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+# GLOBAL VARIABLES/CONSTANTS
+# ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+#
+
+# ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+# CLASS Queue
+# ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+class Queue(object):
+    _initialised: bool;
+    values: List[int];
+
+    def __init__(self):
+        self._initialised = False;
+
+    def INIT(self):
+        self.values = [];
+        self._initialised = True;
+
+    def EMPTY(self) -> bool:
+        return not self._initialised or len(self.values) == 0;
+
+    def ENQUEUE(self, x: int):
+        if not self._initialised:
+            raise Exception('Queue not initialised!')
+        self.values.append(x);
+
+    def FRONT(self) -> int:
+        if self.EMPTY():
+            raise Exception('Cannot read from empty queue!')
+        return self.values[0];
+
+    def DEQUEUE(self) -> int:
+        if self.EMPTY():
+            raise Exception('Cannot remove from empty queue!')
+        self.values = self.values[1:];
+
+    def __str__(self) -> str:
+        if len(self.values) == 0:
+            return '-';
+        return ', '.join([str(x) for x in self.values]);

code/python/src/data_structures/stacks.py

@@ -18,26 +18,33 @@ from local.typing import *;
 # ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
 class Stack(object):
+    _initialised: bool;
     values: List[int];
 
+    def __init__(self):
+        self._initialised = False;
+
     def INIT(self):
         self.values = [];
+        self._initialised = True;
 
     def EMPTY(self) -> bool:
-        return len(self.values) == 0;
+        return not self._initialised or len(self.values) == 0;
 
     def PUSH(self, x: int):
+        if not self._initialised:
+            raise Exception('Stack not initialised!');
         self.values.append(x);
 
     def TOP(self) -> int:
         if self.EMPTY():
-            raise Exception('Cannot pop from empty stack!')
+            raise Exception('Cannot read from empty stack!');
         return self.values[-1];
 
     def POP(self) -> int:
-        x = self.TOP()
-        self.values = self.values[:-1]
-        return x
+        if self.EMPTY():
+            raise Exception('Cannot remove from empty stack!');
+        self.values = self.values[:-1];
 
     def __str__(self) -> str:
         if len(self.values) == 0: