View Compilation Error

0_0_17024093_11512.cpp: In function 'int find(int)':
0_0_17024093_11512.cpp:4:14: error: 'f' was not declared in this scope
     if (x != f[x]) f[x] = find(f[x]);
              ^
0_0_17024093_11512.cpp:5:12: error: 'f' was not declared in this scope
     return f[x];
            ^