안정적인 문자열[백준 4889]

https://www.acmicpc.net/problem/4889

 

def count_operations_to_stable(s):
    stack = []
    operations = 0
    
    for char in s:
        if char == '{':
            stack.append(char)
        else:  # char == '}'
            if stack:
                stack.pop()
            else:
                operations += 1
                stack.append('{')
    
    operations += len(stack) // 2
    
    return operations

test_case_number = 1
while True:
    input_string = input().strip()
    if input_string.startswith('-'):
        break
    
    result = count_operations_to_stable(input_string)
    print(f"{test_case_number}. {result}")
    test_case_number += 1