Compilare: user.cpp: In function ‘void tarjan(int)’: user.cpp:16:9: warning: unused variable ‘i’ [-Wunused-variable] int i, fiu; ^ user.cpp: In function ‘int main()’: user.cpp:68:24: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for ( j = 0; j < S[ i ].size(); ++j ) { ~~^~~~~~~~~~~~~~~ user.cpp:53:27: warning: unused variable ‘nod’ [-Wunused-variable] int n, m, i, j, x, y, nod, fiu; ^~~ user.cpp:53:32: warning: unused variable ‘fiu’ [-Wunused-variable] int n, m, i, j, x, y, nod, fiu; ^~~ user.cpp:50:36: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen( "ctc.in", "r", stdin ); ^ user.cpp:51:38: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen( "ctc.out", "w", stdout ); ^ user.cpp:55:27: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf( "%d%d", &n,&m ); ^ user.cpp:57:31: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf( "%d%d", &x,&y ); ^