题解 | #表达式求值#

import sys
import re

p  = r"[\+]+"
p0 = r"\([\.0-9\+\-\*\/]+\)"
p1 = r"(\-?[\.0-9]+)([\*\/]{1})(\-?[\.0-9]+)"
p2 = r"(\-?[\.0-9]+)([\+\-]{1})(\-?[\.0-9]+)"

# 按照括号、乘除、加减的顺序进行递归，需要注意的就是减号既可以是单目运算符也可以是二目运算符。

def run(a: str):
    if a.isdigit() or (a[1:].isdigit() and a[0]=="-"):
        return a
    a0 = re.search(p0, a)
    if a0:
        s, e = a0.start(0), a0.end(0)
        b = run(a[s+1:e-1])
        a = a[:s]+b+a[e:]
        return run(a)
    a0 = re.search(p1, a)
    if a0:
        s = a0.start(1)
        e = a0.end(3)
        if a0.groups()[1] == "*":
            b = str(int(a0.groups()[0])*int(a0.groups()[2]))
        elif a0.groups()[1] == "/":
            b = str(int(a0.groups()[0])/int(a0.groups()[2]))
        if len(a[:s]) > 0 and a[s-1].isdigit() and b[0].isdigit():
            b = "+"+b
        a = a[:s]+b+a[e:]
        return run(a)
    a0 = re.search(p2, a)
    if a0:
        s = a0.start(1)
        e = a0.end(3)
        if a0.groups()[1] == "+":
            b = str(int(a0.groups()[0])+int(a0.groups()[2]))
        elif a0.groups()[1] == "-":
            b = str(int(a0.groups()[0])-int(a0.groups()[2]))
        if len(a[:s]) > 0 and a[s-1].isdigit() and b[0].isdigit():
            b = "+"+b
        a = a[:s]+b+a[e:]
        return run(a)
    return a

for line in sys.stdin:
    a = line.strip()
    print(int(run(a)))