1 #include <stdio.h>
2 #include <string.h>
3
4 const int N = 256;
5 char buf[N], optr[N];
6 int opnd[N];
7 int opndtop,optrtop;
8
9 bool isDigit(char ch)
10 {
11 return ch >='0' && ch <='9';
12 }
13
14 int pri(char op)
15 {
16 if (op=='(') return 0;
17 if (op=='+'|| op=='-') return 1;
18 if (op=='*'|| op=='/') return 2;
19 }
20
21 void calculate()
22 {
23 int x,y;
24 y = opnd[--opndtop];
25 x = opnd[--opndtop];
26 char op = optr[--optrtop];
27 if (op == '+') x+=y;
28 if (op == '-') x-=y;
29 if (op == '*') x*=y;
30 if (op == '/') x/=y;
31 opnd[opndtop++] = x;
32 }
33
34 int readnum(int &i)
35 {
36 int ret = 0;
37 while (isDigit(buf[i]))
38 {
39 ret=ret*10+buf[i++]-'0';
40 }
41 return ret;
42 }
43
44 int main()
45 {
46 scanf("%s",buf+1);
47 buf[0]='(';
48 int len = strlen(buf);
49 buf[len] = ')';
50 buf[len+1] = '\0';
51 opndtop = optrtop = 0;
52 for (int i=0; buf[i]!='\0';)
53 {
54 if (isDigit(buf[i]))
55 {
56 int x = readnum(i);
57 opnd[opndtop++] = x;
58 }
59 else
60 {
61 char op = buf[i];
62 if (op=='(')
63 optr[optrtop++] = op;
64 else if (op==')')
65 {
66 while (optr[optrtop-1]!='(')
67 {
68 calculate();
69 }
70 optrtop--;
71 }
72 else
73 {
74 while (pri(op)<pri(optr[optrtop-1]))
75 {
76 calculate();
77 }
78 optr[optrtop++] = op;
79 }
80 i++;
81 }
82 }
83 printf("%d\n",opnd[opndtop-1]);
84 return 0;
85 }
