제출 #79510

#제출 시각아이디문제언어결과실행 시간메모리
79510AngelKnowsNetwork (BOI15_net)C++14
0 / 100
2 ms508 KiB
#include <bits/stdc++.h> using namespace std; #define FOR(i,n) for (int i=1;i<=n;i++) #define REP(i,a,b) for (int i=a;i<=b;i++) #define pb push_back #define fi first #define se second #define pi pair<int,int> #define mp make_pair #define sz(x) ((int)(x).size()) typedef long long ll; const int inf=0x3f3f3f3f; const ll linf=1e18; const int N=500000+10; const double eps=1e-5; const int mo=1e9+7; int n; struct edge { int to,nxt; } e[2*N]; int head[N]; int tot; int d[N]; int cnt; int leaves[N]; void insert(int x,int y) { e[++tot].to=y,e[tot].nxt=head[x],head[x]=tot; e[++tot].to=x,e[tot].nxt=head[y],head[y]=tot; } void dfs(int x,int fa) { int y; bool leaf=1; for (int i=head[x];i;i=e[i].nxt) { y=e[i].to; if (y!=fa) { dfs(y,x); leaf=0; } } cnt+=leaf; if (leaf) leaves[cnt]=x; } int main() { std::ios::sync_with_stdio(false); cin.tie(0); cout.tie(0); //freopen("in.txt","r",stdin); //freopen("out.txt","w",stdout); scanf("%d",&n); int x,y; FOR(i,n-1) { scanf("%d %d",&x,&y); ++d[x],++d[y]; insert(x,y); } int root=0; FOR(i,n) if (d[i]!=1) { dfs(i,0); root=i; break; } int ans=(cnt-1)/2+1; printf("%d\n",ans); for (int i=1;i<=cnt;i+=2) { if (i==cnt) { printf("%d %d\n",leaves[i],root); } else printf("%d %d\n",leaves[i],leaves[i+1]); } return 0; }

컴파일 시 표준 에러 (stderr) 메시지

net.cpp: In function 'int main()':
net.cpp:55:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d",&n);
     ~~~~~^~~~~~~~~
net.cpp:58:11: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
      scanf("%d %d",&x,&y);
      ~~~~~^~~~~~~~~~~~~~~
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