rubenmarques-dev
diff --git a/‎pygorithm/data_structures/__init__.py‎ b/‎pygorithm/data_structures/__init__.py‎
diff --git a/‎pygorithm/data_structures/stack.py‎
Lines changed: 114 additions & 0 deletions b/‎pygorithm/data_structures/stack.py‎
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+# Author: OMKAR PATHAK
+# Created On: 3rd August July 2017
+
+# stack implementation
+class Stack(object):
+    '''
+    size    : return the current size of the stack
+    push    : push an item into the stack
+    pop     : pop the topmost item from the stack
+    peek    : return the topmost element of the stack
+    isEmpty : check if the stack is empty
+
+    '''
+
+    def __init__(self, limit = 10):
+        '''
+        @param : limit: the stack size
+        '''
+        self.stack = []
+        self.limit = limit
+
+    # for printing the stack contents
+    def __str__(self):
+        return ' '.join([str(i) for i in self.stack])
+
+    # for pushing an element on to the stack
+    def push(self, data):
+        if len(self.stack) >= self.limit:
+            return -1       # indicates stack overflow
+        else:
+            self.stack.append(data)
+
+    # for popping the uppermost element
+    def pop(self):
+        if len(self.stack) <= 0:
+            return -1       # indicates stack underflow
+        else:
+            return self.stack.pop()
+
+    # for peeking the top-most element of the stack
+    def peek(self):
+        if len(self.stack) <= 0:
+            return -1       # stack underflow
+        else:
+            return self.stack[len(self.stack) - 1]
+
+    # to check if stack is empty
+    def isEmpty(self):
+        return self.stack == []
+
+    # for checking the size of stack
+    def size(self):
+        return len(self.stack)
+
+    # easily retrieve the source code of the Stack class
+    def get_code(self):
+        import inspect
+        return inspect.getsource(Stack)
+
+class InfixToPostfix(object):
+    '''
+    infix_to_postfix : get the postfix of the given infix expression
+
+    '''
+
+    def __init__(self, expression = [], stack = None):
+        '''
+        @param: expression : the infix expression to be converted to postfix
+        @param: stack      : stack to perform infix to postfix operation
+        '''
+        self.myExp = list(expression)
+        self.myStack = stack
+
+    # function to check whether the given character of the expression is operand
+    def _isOperand(self, char):
+        return (ord(char) >= ord('a') and ord(char) <= ord('z')) or (ord(char) >= ord('A') and ord(char) <= ord('Z'))
+
+    # self defined precedence for each operator
+    def _precedence(self, char):
+        if char == '+' or char == '-':
+            return 1
+        elif char == '*' or char  == '/':
+            return 2
+        elif char == '^':
+            return 3
+        else:
+            return -1
+
+    # function to convert infix to postfix 
+    def infix_to_postfix(self):
+        postFix = []
+        for i in range(len(self.myExp)):
+            if (self._isOperand(self.myExp[i])):
+                postFix.append(self.myExp[i])
+            elif(self.myExp[i] == '('):
+                self.myStack.push(self.myExp[i])
+            elif(self.myExp[i] == ')'):
+                topOperator = self.myStack.pop()
+                while(not self.myStack.isEmpty() and topOperator != '('):
+                    postFix.append(topOperator)
+                    topOperator = self.myStack.pop()
+            else:
+                while (not self.myStack.isEmpty()) and (self._precedence(self.myExp[i]) <= self._precedence(self.myStack.peek())):
+                    postFix.append(self.myStack.pop())
+                self.myStack.push(self.myExp[i])
+
+        while(not self.myStack.isEmpty()):
+            postFix.append(self.myStack.pop())
+        return ' '.join(postFix)
+
+    # easily retrieve the source code of the Stack class
+    def get_code(self):
+        import inspect
+        return inspect.getsource(InfixToPostfix)