Compilare: user.cpp: In function ‘int main()’: user.cpp:130:33: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j = 0; j < a[i].size(); j++) ^ user.cpp:131:40: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int k = 0; k < l[a[i][j]].size(); k++) ^ user.cpp:140:33: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j = 0; j < a[i].size(); j++) ^ user.cpp:75:35: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("puzzle2.in", "r", stdin); ^ user.cpp:76:37: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("puzzle2.out", "w", stdout); ^ user.cpp:77:23: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d", &n, &m); ^ user.cpp:79:24: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d", &x, &y); ^ user.cpp: In function ‘void oneLine()’: user.cpp:22:18: warning: ‘v’ may be used uninitialized in this function [-Wmaybe-uninitialized] if(!used[l[v][0]]) ^