Compilare: user.cpp: In function ‘int valid1()’: user.cpp:16:15: warning: statement has no effect [-Wunused-value] for(c1; c1 <= c2; ++c1) { ^ user.cpp:27:15: warning: statement has no effect [-Wunused-value] for(c1; c1 >= c2; c1--) { ^ user.cpp: In function ‘int valid_1()’: user.cpp:45:15: warning: statement has no effect [-Wunused-value] for(c1; c1 <= c2; ++c1) { ^ user.cpp:55:15: warning: statement has no effect [-Wunused-value] for(c1; c1 >= c2; c1--) { ^ user.cpp:43:9: warning: unused variable ‘k’ [-Wunused-variable] int k, nr1 = 0, nr0 = 0, i; ^