View Compilation Error

0_0_31829317_4990.cpp: In function 'void init()':
0_0_31829317_4990.cpp:18:3: error: 'rank_' was not declared in this scope
   rank_[i]=0;
   ^
0_0_31829317_4990.cpp: In function 'void unite(int, int)':
0_0_31829317_4990.cpp:37:5: error: 'rank_' was not declared in this scope
  if(rank_[x]<rank_[y])
     ^
0_0_31829317_4990.cpp:41:5: error: 'rank_' was not declared in this scope
  if(rank_[x]==rank_[y])
     ^