Compilare: user.cpp: In function ‘int bf_extend(const std::vector<int>&, int, int)’: user.cpp:13:48: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(j = dist; 1 <= i - j && i + j < V.size() && V[i + j] == V[i - j]; j++); ^ user.cpp: In function ‘std::vector<int> manacher(const std::vector<int>&)’: user.cpp:21:40: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i = 1, r = ir = -1; i < V.size(); i++) { ^ user.cpp:19:12: warning: unused variable ‘j’ [-Wunused-variable] int i, j, r, ir; ^ user.cpp: In function ‘int get_area_column(const std::vector<int>&)’: user.cpp:45:29: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i = 1; i < col.size(); i++) { ^ user.cpp:69:29: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i = 1; i < col.size(); i++) { ^