View Compilation Error

0_0_37295614_2066.cpp:6:1: error: expected unqualified-id before '{' token
 {
 ^
0_0_37295614_2066.cpp:9:2: error: 'a' does not name a type
 }a[100];
  ^
0_0_37295614_2066.cpp: In function 'bool cmp(s, s)':
0_0_37295614_2066.cpp:10:12: error: 'a' has incomplete type
 bool cmp(s a,s b)
            ^
0_0_37295614_2066.cpp:5:8: error: forward declaration of 'struct s'
 struct s;
        ^
0_0_37295614_2066.cpp:10:16: error: 'b' has incomplete type
 bool cmp(s a,s b)
                ^
0_0_37295614_2066.cpp:5:8: error: forward declaration of 'struct s'
 struct s;
        ^
0_0_37295614_2066.cpp: In function 'int main()':
0_0_37295614_2066.cpp:21:18: error: 'a' was not declared in this scope
    scanf("%s %d",a[i].color,&a[i].num)
                  ^
0_0_37295614_2066.cpp:23:8: error: 'a' was not declared in this scope
   sort(a,a+n,cmp);
        ^