View Compilation Error

0_0_25449852_318.cpp: In function 'int main()':
0_0_25449852_318.cpp:33:24: error: 'class std::stack<char>' has no member named 'length'
    for(int i = 0;i < l.length(); i++){
                        ^
0_0_25449852_318.cpp:34:27: error: invalid operands of types '<unresolved overloaded function type>' and 'char' to binary 'operator=='
     if(!l.empty()&&l.top=='('&&s[i]==')'){
                           ^
0_0_25449852_318.cpp:44:6: error: 'a' was not declared in this scope
      a[k].l++;
      ^
0_0_25449852_318.cpp:47:6: error: 'a' was not declared in this scope
      a[k].r++;
      ^
0_0_25449852_318.cpp:51:8: error: 'a' was not declared in this scope
   sort(a,a+k,cmp);
        ^
0_0_25449852_318.cpp:51:12: error: 'k' was not declared in this scope
   sort(a,a+k,cmp);
            ^