Compilare: user.cpp: In function ‘bool check(int)’: user.cpp:45:33: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(val != p[i][j + 1]) ^ user.cpp:51:33: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(val != p[i][j - 1]) ^ user.cpp:57:33: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(val != p[i + 1][j]) ^ user.cpp:63:33: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(val != p[i - 1][j]) ^ user.cpp: In function ‘int main()’: user.cpp:89:37: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(val != p[i][j + 1]) ^ user.cpp:95:37: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(val != p[i][j - 1]) ^ user.cpp:101:37: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(val != p[i + 1][j]) ^ user.cpp:107:37: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(val != p[i - 1][j]) ^