Eroare de compilare: user.cpp:2:22: error: algorithm.h: No such file or directory user.cpp:3:19: error: vector.h: No such file or directory user.cpp: In function ‘int valid(int)’: user.cpp:14: warning: comparison between signed and unsigned integer expressions user.cpp:15: error: request for member ‘size’ in ‘i’, which is of non-class type ‘int’ user.cpp:15: warning: comparison between signed and unsigned integer expressions user.cpp:17: error: request for member ‘size’ in ‘i’, which is of non-class type ‘int’ user.cpp:18: error: request for member ‘size’ in ‘i’, which is of non-class type ‘int’ user.cpp:19: error: request for member ‘size’ in ‘i’, which is of non-class type ‘int’ user.cpp:15: warning: suggest explicit braces to avoid ambiguous ‘else’ user.cpp: In function ‘void back(int)’: user.cpp:23: warning: unused variable ‘p_val’ user.cpp:23: warning: unused variable ‘i’ user.cpp: In function ‘int main()’: user.cpp:37: warning: comparison between signed and unsigned integer expressions user.cpp:40: error: ‘system’ was not declared in this scope