View Compilation Error

0_0_30173122_24622.cpp: In function 'int find(int)':
0_0_30173122_24622.cpp:13:12: error: 'pre' was not declared in this scope
     while (pre[r]!=r)
            ^
0_0_30173122_24622.cpp:19:11: error: 'pre' was not declared in this scope
         j=pre[i];
           ^