【CF】328 D. Super M

这种图论题已经变得简单了。。。

 /* D */
 #include <iostream>
 #include <string>
 #include <map>
 #include <queue>
 #include <set>
 #include <stack>
 #include <vector>
 #include <deque>
 #include <algorithm>
 #include <cstdio>
 #include <cmath>
 #include <ctime>
 #include <cstring>
 #include <climits>
 #include <cctype>
 #include <cassert>
 #include <functional>
 #include <iterator>
 #include <iomanip>
 using namespace std;
 //#pragma comment(linker,"/STACK:102400000,1024000")

 #define sti                set<int>
 #define stpii            set<pair<int, int> >
 #define mpii            map<int,int>
 #define vi                vector<int>
 #define pii                pair<int,int>
 #define vpii            vector<pair<int,int> >
 #define rep(i, a, n)     for (int i=a;i<n;++i)
 #define per(i, a, n)     for (int i=n-1;i>=a;--i)
 #define clr                clear
 #define pb                 push_back
 #define mp                 make_pair
 #define fir                first
 #define sec                second
 #define all(x)             (x).begin(),(x).end()
 #define SZ(x)             ((int)(x).size())
 #define lson            l, mid, rt<<1
 #define rson            mid+1, r, rt<<1|1

 const int maxn = ;
 vi vc[maxn], vc2[maxn];
 bool visit[maxn];
 bool mark[maxn];
 int markp[maxn], pre[maxn];
 int mx[maxn], mx_[maxn];
 int n, m, length = ;
 int mn = INT_MAX, ans = INT_MAX;

 void bfs(int s) {
     queue<int> Q;
     int u, v, sz;

     Q.push(s);
     visit[s] = true;
     pre[s] = ;

     while (!Q.empty()) {
         u = Q.front();
         Q.pop();
         sz = SZ(vc[u]);
         rep(i, , sz) {
             v = vc[u][i];
             if (!visit[v]) {
                 visit[v] = true;
                 pre[v] = u;
                 Q.push(v);
             }
         }
     }
 }

 void dfs3(int v) {
     if (visit[v])
         return;

     visit[v] = true;
     int u = pre[v];

     length += ;
     vc2[u].pb(v);
     vc2[v].pb(u);
     if (u)
         dfs3(u);
 }

 void dfs(int u, int fa) {
     int v, sz = SZ(vc2[u]);

     mx[u] = mx_[u] = ;
     rep(i, , sz) {
         v = vc2[u][i];
         if (v == fa)
             continue;

         dfs(v, u);
         if (mx[v]+ > mx[u]) {
             mx_[u] = mx[u];
             mx[u] = mx[v] + ;
         } else if (mx[v]+ > mx_[u]) {
             mx_[u] = mx[v]+;
         }
     }

     #ifndef ONLINE_JUDGE
         printf("u = %d, mx[u] = %d, mx_[u] = %d\n", u, mx[u], mx_[u]);
     #endif
 }

 void dfs2(int u, int fa, int pmx) {
     int v, sz = SZ(vc2[u]);
     int cmx = max(mx[u], pmx), tmp;

     if (length-cmx < mn) {
         mn = length - cmx;
         ans = u;
     } else if (length-cmx==mn && u<ans) {
         ans = u;
     }

     rep(i, , sz) {
         v = vc2[u][i];
         if (v == fa)
             continue;

         if (mx[v]+ == mx[u]) {
             tmp = max(pmx, mx_[u])+;
         } else {
             tmp = max(pmx, mx[u])+;
         }

         dfs2(v, u, tmp);
     }
 }

 int main() {
     ios::sync_with_stdio(false);
     #ifndef ONLINE_JUDGE
         freopen("data.in", "r", stdin);
         freopen("data.out", "w", stdout);
     #endif

     int u, v, x;

     scanf("%d %d", &n, &m);
     rep(i, , n) {
         scanf("%d %d", &u, &v);
         vc[u].pb(v);
         vc[v].pb(u);
     }

     rep(i, , m) {
         scanf("%d", &x);
         markp[i] = x;
         mark[x] = true;
     }

     bfs(x);
     memset(visit, false, sizeof(visit));
     visit[x] = true;
     rep(i, , m)
         dfs3(markp[i]);
     dfs(x, );
     dfs2(x, , );

     printf("%d\n%d\n", ans, mn);

     #ifndef ONLINE_JUDGE
         printf("time = %d.\n", (int)clock());
     #endif

     return ;
 }