View Compilation Error

0_0_19060972_5502.cpp: In member function 'void VectorArrayBasedGraphics::CombineSamePropertyNodes(T2*, long long int, long long int)':
0_0_19060972_5502.cpp:153:36: error: 'tree' was not declared in this scope
    for (vector<int>::iterator it = tree[i].begin(); it != tree[i].end();){
                                    ^