View Compilation Error

0_0_33921618_3846.cpp: In function 'void kruskal()':
0_0_33921618_3846.cpp:25:15: error: 'a' was not declared in this scope
   int k=fin_d(a[i].u);
               ^
0_0_33921618_3846.cpp: In function 'int main()':
0_0_33921618_3846.cpp:53:27: error: 'memset' was not declared in this scope
   memset(vis,0,sizeof(vis));
                           ^
0_0_33921618_3846.cpp:67:9: error: 'ans' was not declared in this scope
   cout<<ans<<" "<<ans1<<endl;
         ^