Compilare: user.cpp: In function ‘int main()’: user.cpp:144:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] int s = a[0].size() == r ? c : r; ^ user.cpp:146:33: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j = 0; j < a[0].size(); j++) ^ user.cpp:147:40: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int k = 0; k < l[a[i][j]].size(); k++) ^ user.cpp:155:33: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j = 0; j < a[0].size(); j++) ^ user.cpp:92:35: 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:93:37: 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:94:23: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d", &n, &m); ^ user.cpp:96:24: 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 twoLines()’: user.cpp:33:6: warning: ‘v1’ may be used uninitialized in this function [-Wmaybe-uninitialized] int v1, v2; ^