Compilare: user.cpp: In function ‘void read()’: user.cpp:28:18: warning: unused variable ‘c’ [-Wunused-variable] int x, y, i, c; ^ user.cpp: In function ‘void solve()’: user.cpp:137:45: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (j = 0; j < color [i].size (); j ++) ^ user.cpp:141:45: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (j = 1; j < color [i].size (); j ++) { ^