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Author: Sagar Paul

Write a function in python that can reverse a string using stack data structure.py

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+'''
+Write a function in python that can reverse a string using stack data structure.
+
+reverse_string("We will conquere COVID-19") should return "91-DIVOC ereuqnoc lliw eW"
+
+'''
+
+from collections import deque
+
+class Stack:
+def init(self):
+self.container = deque()
+
+def push(self, val):
+    self.container.append(val)
+
+def pop(self):
+    return self.container.pop()
+
+def peek(self):
+    return self.container[-1]
+
+def is_empty(self):
+    return len(self.container) == 0
+
+def size(self):
+    return len(self.container)
+
+def reverse_string(s):
+stack = Stack()
+
+for ch in s:
+    stack.push(ch)
+
+rstr = ''
+while stack.size()!=0:
+    rstr += stack.pop()
+
+return rstr
+
+if name == 'main':
+print(reverse_string("We will conquere COVI-19"))
+print(reverse_string("I am the king"))

Write a function in python that checks if paranthesis in the string are balanced or not. Possible parantheses are "{}',"()" or "[]".py

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+'''
+Write a function in python that checks if paranthesis in the string are balanced or not. Possible parantheses are "{}',"()" or "[]".
+
+exmple:
+
+is_balanced("({a+b})") --> True
+is_balanced("))((a+b}{") --> False
+is_balanced("((a+b))") --> True
+is_balanced("))") --> False
+is_balanced("[a+b](x+2y){gg+kk}") --> True
+
+'''
+from collections import deque
+
+class Stack:
+def init(self):
+self.container = deque()
+
+def push(self, val):
+    self.container.append(val)
+
+def pop(self):
+    return self.container.pop()
+
+def peek(self):
+    return self.container[-1]
+
+def is_empty(self):
+    return len(self.container) == 0
+
+def size(self):
+    return len(self.container)
+
+def is_match(ch1, ch2):
+match_dict = {
+')': '(',
+']': '[',
+'}': '{'
+}
+return match_dict[ch1] == ch2
+
+def is_balanced(s):
+stack = Stack()
+for ch in s:
+if ch=='(' or ch=='{' or ch == '[':
+stack.push(ch)
+if ch==')' or ch=='}' or ch == ']':
+if stack.size()==0:
+return False
+if not is_match(ch,stack.pop()):
+return False
+
+return stack.size()==0
+
+if name == 'main':
+print(is_balanced("({a+b})"))
+print(is_balanced("))((a+b}{"))
+print(is_balanced("((a+b))"))
+print(is_balanced("((a+g))"))
+print(is_balanced("))"))
+print(is_balanced("[a+b](x+2y){gg+kk}"))