View Compilation Error

0_0_16489044_9740.cpp: In function 'int find(int)':
0_0_16489044_9740.cpp:16:10: error: 'f' was not declared in this scope
  if(x == f[x]) return x;
          ^
0_0_16489044_9740.cpp:17:10: error: 'f' was not declared in this scope
  if(x != f[x]) f[x] = find(f[x]);
          ^
0_0_16489044_9740.cpp:18:9: error: 'f' was not declared in this scope
  return f[x];
         ^