题意：bool表达式求值，V：true；F：false

题解：堆栈+优先级判定

View Code 
 1 #include<cstdio>
 2 #include<cstring>
 3 #include<algorithm>
 4 #include<cctype>
 5 using namespace std;
 6 const int N=1000;
 7 char comp(char a,char b)
 8 {
 9     if(b=='\0')
10     {
11         if(a=='\0')
12             return '=';
13         else
14             return '>';
15     }
16     else if(a=='\0')
17         return '<';
18     else if(b=='(')
19         return '<';
20     else if(b==')')
21     {
22         if(a=='(')
23             return '=';
24         else
25             return '>';
26     }
27     else if(a=='(')
28         return '<';
29     else
30         return '>';
31 }
32 bool cac(bool a,bool b,char op)
33 {
34     if(op=='|')
35         return a||b;
36     else if(op=='&')
37         return a&&b;
38 }
39 bool solve(char s[])
40 {
41     int len=strlen(s),optop=0,botop=0,i=0;
42     char opstk[N];
43     bool bostk[N];
44     opstk[optop++]='\0';
45     while(s[i]!='\0'||opstk[optop-1]!='\0')
46     {
47         if(s[i]==' '||s[i]=='\t')
48         {
49             i++;
50             continue;
51         }
52         else if(s[i]=='!'||s[i]=='(')
53             opstk[optop++]=s[i++];
54         else if(s[i]=='V'||s[i]=='F')
55             bostk[botop++]=(s[i]=='V'),i++;
56         else
57         {
58             switch(comp(opstk[optop-1],s[i]))
59             {
60                 case '>':
61                     if(opstk[optop-1]=='!')
62                     {
63                         optop--;
64                         bostk[botop-1]^=true;
65                     }
66                     else
67                     {
68                         bool b=bostk[--botop],a=bostk[--botop];
69                         char ch=opstk[--optop];
70                         bostk[botop++]=cac(a,b,ch);
71                     }
72                     break;
73                 case '<':
74                     opstk[optop++]=s[i++];
75                     break;
76                 case '=':
77                     optop--;
78                     i++;
79                     break;
80             }
81         }
82     }
83     return bostk[0];
84 }
85 int main()
86 {
87     char s[200];
88     int ca=0;
89     while(gets(s))
90         printf("Expression %d: %c\n",++ca,solve(s)?'V':'F');
91     return 0;
92 }