stack_class.py

# define Stack class with push, pop, peek, is_empty, and size methods
# Stack ADT
class ArrayStack:
    def __init__(self, capacity):
        self.capacity = capacity
        self.array = [None] * capacity
        self.top = -1

    def is_empty(self):
        return self.top == -1
    
    def is_full(self):
        return self.top == self.capacity - 1
    
    def push(self, item):
        if not self.is_full():
            self.top += 1
            self.array[self.top] = item
            print(f"PUSH: {item!r} -> stack is now {self.array[:self.top + 1]}")
        else:
            raise OverflowError("Stack Overflow") # pass
        
    def pop(self):
        if not self.is_empty():
            item = self.array[self.top]
            self.array[self.top] = None
            self.top -= 1
            print(f"POP: {item!r} -> stack is now {self.array[:self.top + 1]}")
            return item
        else:
            raise IndexError("Stack Underflow")
        
    def peek(self):
        if not self.is_empty():
            return self.array[self.top]
        return None
    
    def size(self):
        return self.top + 1
    
# Test the Stack class
def reverse_string(statement):
    print("\n[1] PUSH 단계 ------------------------------")
    st = ArrayStack(len(statement))
    for char in statement:
        st.push(char)

    print("\n[2] POP 단계 ------------------------------")
    out = [] # list
    while not st.is_empty():
        out.append(st.pop())

    result = ''.join(out)
    print(f"\n[3] 최종 결과: {result}")
    return result

if __name__ == "__main__":
    statement = "안녕하세요, 반갑습니다."
    reverse_string(statement)