View Compilation Error

0_0_13822633_19937.cpp: In function 'int Directed_MST(int, int, int)':
0_0_13822633_19937.cpp:77:21: error: 'v' was not declared in this scope
                 pre[v]=u;
                     ^
0_0_13822633_19937.cpp:77:24: error: 'u' was not declared in this scope
                 pre[v]=u;
                        ^