View Compilation Error

0_0_15002824_16759.cpp: In function 'int find(int)':
0_0_15002824_16759.cpp:18:12: error: 'f' was not declared in this scope
     return f[v]==v?v:f[v]=find(f[v]);
            ^
0_0_15002824_16759.cpp: In function 'void merge(int, int)':
0_0_15002824_16759.cpp:22:5: error: 'x' was not declared in this scope
     x = find(a);
     ^
0_0_15002824_16759.cpp:23:5: error: 'y' was not declared in this scope
     y = find(b);
     ^