View Compilation Error

0_0_29396673_9053.cpp: In function 'int find(int)':
0_0_29396673_9053.cpp:36:12: error: 'f' was not declared in this scope
  return n==f[n]?n:f[n]=find(f[n]);
            ^
0_0_29396673_9053.cpp: In function 'void merge(int, int)':
0_0_29396673_9053.cpp:44:3: error: 'f' was not declared in this scope
   f[xx]=yy;
   ^