传参时用了 vec[x].size()-1 编译好想爆了：

[Warning] narrowing conversion of '(son[x].std::vector<_Tp, _Alloc>::size<int, std::allocator<int> >() + 18446744073709551615ull)' from 'std::vector<int>::size_type {aka long long unsigned int}' to 'int' inside { } [-Wnarrowing]