View Compilation Error

0_0_29807559_31328.cpp: In function 'int main()':
0_0_29807559_31328.cpp:31:17: error: invalid types 'int[int]' for array subscript
           c[a[i]].push_back(i);
                 ^
0_0_29807559_31328.cpp:40:24: error: invalid types 'int[int]' for array subscript
              int nx=c[i].size();
                        ^
0_0_29807559_31328.cpp:41:23: error: invalid types 'int[int]' for array subscript
              while(c[i])
                       ^
0_0_29807559_31328.cpp:42:10: error: expected primary-expression before '}' token
          }
          ^