【CF】328 D. Super M

这种图论题已经变得简单了。。。
  1 /* D */
  2 #include <iostream>
  3 #include <string>
  4 #include <map>
  5 #include <queue>
  6 #include <set>
  7 #include <stack>
  8 #include <vector>
  9 #include <deque>
 10 #include <algorithm>
 11 #include <cstdio>
 12 #include <cmath>
 13 #include <ctime>
 14 #include <cstring>
 15 #include <climits>
 16 #include <cctype>
 17 #include <cassert>
 18 #include <functional>
 19 #include <iterator>
 20 #include <iomanip>
 21 using namespace std;
 22 //#pragma comment(linker,"/STACK:102400000,1024000")
 23 
 24 #define sti                set<int>
 25 #define stpii            set<pair<int, int> >
 26 #define mpii            map<int,int>
 27 #define vi                vector<int>
 28 #define pii                pair<int,int>
 29 #define vpii            vector<pair<int,int> >
 30 #define rep(i, a, n)     for (int i=a;i<n;++i)
 31 #define per(i, a, n)     for (int i=n-1;i>=a;--i)
 32 #define clr                clear
 33 #define pb                 push_back
 34 #define mp                 make_pair
 35 #define fir                first
 36 #define sec                second
 37 #define all(x)             (x).begin(),(x).end()
 38 #define SZ(x)             ((int)(x).size())
 39 #define lson            l, mid, rt<<1
 40 #define rson            mid+1, r, rt<<1|1
 41 
 42 const int maxn = 123460;
 43 vi vc[maxn], vc2[maxn];
 44 bool visit[maxn];
 45 bool mark[maxn];
 46 int markp[maxn], pre[maxn];
 47 int mx[maxn], mx_[maxn];
 48 int n, m, length = 0;
 49 int mn = INT_MAX, ans = INT_MAX;
 50 
 51 void bfs(int s) {
 52     queue<int> Q;
 53     int u, v, sz;
 54 
 55     Q.push(s);
 56     visit[s] = true;
 57     pre[s] = 0;
 58 
 59     while (!Q.empty()) {
 60         u = Q.front();
 61         Q.pop();
 62         sz = SZ(vc[u]);
 63         rep(i, 0, sz) {
 64             v = vc[u][i];
 65             if (!visit[v]) {
 66                 visit[v] = true;
 67                 pre[v] = u;
 68                 Q.push(v);
 69             }
 70         }
 71     }
 72 }
 73 
 74 void dfs3(int v) {
 75     if (visit[v])
 76         return;
 77 
 78     visit[v] = true;
 79     int u = pre[v];
 80 
 81     length += 2;
 82     vc2[u].pb(v);
 83     vc2[v].pb(u);
 84     if (u)
 85         dfs3(u);
 86 }
 87 
 88 void dfs(int u, int fa) {
 89     int v, sz = SZ(vc2[u]);
 90     
 91     mx[u] = mx_[u] = 0;
 92     rep(i, 0, sz) {
 93         v = vc2[u][i];
 94         if (v == fa)
 95             continue;
 96         
 97         dfs(v, u);
 98         if (mx[v]+1 > mx[u]) {
 99             mx_[u] = mx[u];
100             mx[u] = mx[v] + 1;
101         } else if (mx[v]+1 > mx_[u]) {
102             mx_[u] = mx[v]+1;
103         }
104     }
105     
106     #ifndef ONLINE_JUDGE
107         printf("u = %d, mx[u] = %d, mx_[u] = %d
", u, mx[u], mx_[u]);
108     #endif
109 }
110 
111 void dfs2(int u, int fa, int pmx) {
112     int v, sz = SZ(vc2[u]);
113     int cmx = max(mx[u], pmx), tmp;
114 
115     if (length-cmx < mn) {
116         mn = length - cmx;
117         ans = u;
118     } else if (length-cmx==mn && u<ans) {
119         ans = u;
120     }
121 
122     rep(i, 0, sz) {
123         v = vc2[u][i];
124         if (v == fa)
125             continue;
126 
127         if (mx[v]+1 == mx[u]) {
128             tmp = max(pmx, mx_[u])+1;
129         } else {
130             tmp = max(pmx, mx[u])+1;
131         }
132 
133         dfs2(v, u, tmp);
134     }
135 }
136 
137 int main() {
138     ios::sync_with_stdio(false);
139     #ifndef ONLINE_JUDGE
140         freopen("data.in", "r", stdin);
141         freopen("data.out", "w", stdout);
142     #endif
143 
144     int u, v, x;
145 
146     scanf("%d %d", &n, &m);
147     rep(i, 1, n) {
148         scanf("%d %d", &u, &v);
149         vc[u].pb(v);
150         vc[v].pb(u);
151     }
152 
153     rep(i, 0, m) {
154         scanf("%d", &x);
155         markp[i] = x;
156         mark[x] = true;
157     }
158 
159     bfs(x);
160     memset(visit, false, sizeof(visit));
161     visit[x] = true;
162     rep(i, 0, m)
163         dfs3(markp[i]);
164     dfs(x, 0);
165     dfs2(x, 0, 0);
166 
167     printf("%d
%d
", ans, mn);
168 
169     #ifndef ONLINE_JUDGE
170         printf("time = %d.
", (int)clock());
171     #endif
172 
173     return 0;
174 }