Compilare: user.cpp: In function ‘int main()’: user.cpp:11:385: warning: unused variable ‘j’ [-Wunused-variable] int n,i,j,k=0;cin>>n;int a,b;for(i=1;i<=n;i++){cin>>a>>b;a+=100;b+=100;f[b]++;v[a].push_back(b);}int nr=0;for(i=0;i<=200;i++){for(auto j:v[i]){x.push_back(j);}if(f[i]>=1){for(auto j:x){f[j]--;}x.clear();k++;}}cout<<k; ^ user.cpp:11:478: warning: unused variable ‘nr’ [-Wunused-variable] int n,i,j,k=0;cin>>n;int a,b;for(i=1;i<=n;i++){cin>>a>>b;a+=100;b+=100;f[b]++;v[a].push_back(b);}int nr=0;for(i=0;i<=200;i++){for(auto j:v[i]){x.push_back(j);}if(f[i]>=1){for(auto j:x){f[j]--;}x.clear();k++;}}cout<<k; ^~ user.cpp:9:37: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("reactivi.in","r",stdin); ^ user.cpp:10:39: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("reactivi.out","w",stdout); ^