ECNUOJ 2574 Principles of Compiler

Principles of Compiler

Time Limit:1000MS Memory Limit:65536KB
Total Submit:473 Accepted:106

Description 

After learnt the Principles of Compiler,partychen thought that he can solve a simple expression problem.So he give you strings of less than 100 characters which strictly adhere to the following grammar (given in EBNF):
    A:= '(' B')'|'x'.
    B:=AC.
    C:={'+'A}.
Can you solve them too?

Input 

The first line of input gives the number of cases, N(1 ≤ N ≤ 100). N test cases follow.
The next N lines will each contain a string as described above.

Output 

For each test case,if the expression is adapt to the EBNF above output “Good”,else output “Bad”.

Sample Input 

3
(x)
(x+(x+x))
()(x)

Sample Output 

Good
Good
Bad

Source

解题：几十万只草泥马呼啸而过，一直没搞懂{+A}的含义

重复 { ... } 也就是说这个是表示+A可以出现0次或多次

 #include <bits/stdc++.h>
 using namespace std;
 const int maxn = ;
 char str[maxn];
 int cur;
 bool A();
 bool B();
 bool C();
 bool A() {
     if(str[cur] == 'x') {
         cur++;
         return true;
     }
      if(str[cur] == '(') {
         cur++;
         if(B() && str[cur] == ')') {
             cur++;
             return true;
         }
     }
     return false;
 }
 bool B() {
     return A() && C();
 }
 bool C() {
     while(str[cur] == '+'){
         cur++;
         if(!A()) return false;
     }
     return true;
 }
 int main() {
     int kase;
     scanf("%d",&kase);
     getchar();
     while(kase--) {
         gets(str);
         cur = ;
         puts(A() && str[cur] == '\0'?"Good":"Bad");
     }
     return ;
 }