Compilare: user.cpp: In function ‘int main()’: user.cpp:41:37: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (_i = 0 ; _i < tmp.size() ; ++_i) ^ user.cpp:55:45: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (_j = 0 ; _j < tmp.size() ; ++_j) ^ user.cpp:14:33: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("cast.in" , "r" , stdin); ^ user.cpp:15:35: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("cast.out" , "w" , stdout); ^ user.cpp:17:27: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] for (scanf("%d" , &tests) ; tests ; --tests) ^ user.cpp:19:21: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d" , &n); ^ user.cpp:26:27: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d" , &c[i][j]); ^