백준 - 1918 : 후위 표기식 (G2)

 1string = list(input())
 2
 3priority = {'(':0, ')':0, '+':1, '-':1, '*':2, '/':2}
 4operator = []
 5result = ''
 6
 7for c in string:
 8    if c.isalpha():
 9        result += c
10    elif c == '(':
11        operator.append(c)
12    elif c == ')':
13        while operator:
14            op = operator.pop()
15            if op == '(':
16                break
17            result += op
18    else:
19        if operator:
20            if priority[operator[-1]] < priority[c]:
21                operator.append(c)
22            else:
23                while operator and priority[operator[-1]] >= priority[c]:
24                    result += operator.pop()
25                operator.append(c)
26        else:
27            operator.append(c)
28while operator:
29    result += operator.pop()
30
31print (result)