Compilare: user.cpp: In function ‘void build_chain(int)’: user.cpp:78:28: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0;i<g[node].size();i++) ^ user.cpp:95:33: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0;i<g[neighbour].size();i++) ^ user.cpp: In function ‘int solve()’: user.cpp:122:33: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(j=0;j<g[i].size();j++) ^ user.cpp:131:38: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(j=0;j<g[special[i]].size();j++) ^ user.cpp: In function ‘int main()’: user.cpp:152:36: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("metrou2.in","r",stdin); ^ user.cpp:153:38: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("metrou2.out","w",stdout); ^ user.cpp:155:24: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d",&n,&m); ^ user.cpp:157:29: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d",&cost[i]); ^ user.cpp:159:28: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d",&a,&b); ^