def calculate(s: str) -> int:
def precedence(op):
"""定义运算符优先级：乘除 > 加减"""
return 2 if op in ('*', '/') else 1
def apply_op(a: int, b: int, op: str) -> int:
"""执行运算"""
if op == '+':
return a + b
elif op == '-':
return a - b
elif op == '*':
return a * b
elif op == '/':
return a // b 整数除法，可根据需求改为浮点数除法
预处理：去除空格，大括号转为小括号（仅支持小括号逻辑）
s = s.replace(' ', '').replace('{', '(').replace('}', ')')
nums = [] 数字栈
ops = [] 运算符栈
i = 0
n = len(s)
while i < n:
if s[i].isdigit():
处理多位数（如123）
num = 0
while i < n and s[i].isdigit():
num = num * 10 + int(s[i])
i += 1
nums.append(num)
elif s[i] == '(':
ops.append(s[i])
i += 1
elif s[i] == ')':
遇到右括号，弹出运算符直到左括号
while ops and ops[-1] != '(':
b = nums.pop()
a = nums.pop()
op = ops.pop()
nums.append(apply_op(a, b, op))
ops.pop() 弹出左括号
i += 1
elif s[i] in ('+', '-', '*', '/'):
处理运算符优先级：当前运算符优先级≤栈顶时，先执行栈顶运算
while ops and ops[-1] != '(' and precedence(ops[-1]) >= precedence(s[i]):
b = nums.pop()
a = nums.pop()
op = ops.pop()
nums.append(apply_op(a, b, op))
ops.append(s[i])
i += 1
else:
raise ValueError("无效字符：" + s[i])
处理剩余运算符
while ops:
b = nums.pop()
a = nums.pop()
op = ops.pop()
nums.append(apply_op(a, b, op))
return nums[0]
