Compilare: user.cpp: In function ‘int main()’: user.cpp:37:25: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=1; i<s.size(); ++i) { ^ user.cpp: In function ‘int cb(int)’: user.cpp:21:25: warning: ‘r’ may be used uninitialized in this function [-Wmaybe-uninitialized] for(;r>0 && sp[i]-sp[r]<=k; --r); ^