[hdu4123]dfs区间化+RMQ

题意：给一个树编号0~n-1，一个数组a[i]为节点i在树上走的最大距离（不重复点），然后求最大的区间，使得区间最大差异小于某个值。dfs求出每个数组，同时区间化。枚举区间左边界，右边界同样递增，类似单调队列，区间最值用RMQ查询（常数小）。

 #pragma comment(linker, "/STACK:10240000,10240000")

 #include <iostream>
 #include <cstdio>
 #include <algorithm>
 #include <cstdlib>
 #include <cstring>
 #include <map>
 #include <queue>
 #include <deque>
 #include <cmath>
 #include <vector>
 #include <ctime>
 #include <cctype>
 #include <set>

 using namespace std;

 #define mem0(a) memset(a, 0, sizeof(a))
 #define lson l, m, rt << 1
 #define rson m + 1, r, rt << 1 | 1
 #define define_m int m = (l + r) >> 1
 #define Rep(a, b) for(int a = 0; a < b; a++)
 #define lowbit(x) ((x) & (-(x)))
 #define constructInt4(name, a, b, c, d) name(int a = 0, int b = 0, int c = 0, int d = 0): a(a), b(b), c(c), d(d) {}
 #define constructInt3(name, a, b, c) name(int a = 0, int b = 0, int c = 0): a(a), b(b), c(c) {}
 #define constructInt2(name, a, b) name(int a = 0, int b = 0): a(a), b(b) {}

 typedef double db;
 typedef long long LL;
 typedef pair<int, int> pii;
 typedef multiset<int> msi;
 typedef multiset<int>::iterator msii;
 typedef set<int> si;
 typedef set<int>::iterator sii;
 typedef vector<int> vi;

 const int dx[] = {, , -, , , , -, -};
 const int dy[] = {, -, , , -, , , -};
 const int maxn = 1e5 + ;
 const int maxm = 1e5 + ;
 const int maxv = 1e7 + ;
 const int MD = 1e9 +;
 const int INF = 1e9 + ;
 const double PI = acos(-1.0);
 const double eps = 1e-;

 template<class T> struct MonotoneQueue{
     deque<T> Q;
     MonotoneQueue<T>() { Q.clear(); }
     void clear() { Q.clear(); }
     bool empty() { return Q.empty(); }
     void add_back(T x) { while (!Q.empty() && !(Q.back() < x)) Q.pop_back(); Q.push_back(x); }
     void pop_front() { Q.pop_front(); }
     T back2() { if(Q.size() < ) return T(); return *(Q.end() - ); }
     T front() { return Q.front(); }
 };

 template<class edge> struct Graph {
     vector<vector<edge> > adj;
     Graph(int n) { adj.clear(); adj.resize(n + ); }
     Graph() { adj.clear(); }
     void resize(int n) { adj.resize(n + ); }
     void add(int s, edge e){ adj[s].push_back(e); }
     void del(int s, edge e) { adj[s].erase(find(iter(adj[s]), e)); }
     void clear() { adj.clear(); }
     vector<edge>& operator [](int t) { return adj[t]; }
 };

 Graph<int> G, W;

 int maxd, id, d, n, m;
 int dis[maxn], t[maxn], maxf[maxn][], minf[maxn][];
 bool vis[maxn];

 void DFS(int node) {
     vis[node] = true;
     dis[node] = max(dis[node], d);
     if (d > maxd) {
         maxd = d;
         id = node;
     }
     for (int i = ; i < G[node].size(); i++) {
         int u = G[node][i];
         if (!vis[u]) {
             d += W[node][i];
             DFS(u);
             d -= W[node][i];
         }
     }
 }

 void InitRMQ() {
     for (int i = ; i <= n; i++) maxf[i][] = minf[i][] = dis[i];
     for (int j = ; ( << j) <= n; j++) {
         for (int i = ; i + ( << j) -  <= n; i++) {
             maxf[i][j] = max(maxf[i][j - ], maxf[i + ( << (j - ))][j - ]);
             minf[i][j] = min(minf[i][j - ], minf[i + ( << (j - ))][j - ]);
         }
     }
 }
 int RMQ_max(int L, int R) {
     int x = t[R - L + ];
     return max(maxf[L][x], maxf[R - ( << x) + ][x]);
 }
 int RMQ_min(int L, int R) {
     int x = t[R - L + ];
     return min(minf[L][x], minf[R - ( << x) + ][x]);
 }

 int solve(int q) {
     int L = , ans = ;
     for (int R = ; R <= n; R++) {
         while (RMQ_max(L, R) - RMQ_min(L, R) > q) L++;
         ans = max(ans, R - L + );
     }
     return ans;
 }

 int main() {
     //freopen("in.txt", "r", stdin);
     for (int i = ; i <= ; i++) {
         int j = ;
         while (( << (j + )) <= i) j++;
         t[i] = j;
     }
     while (cin >> n >> m, n || m) {
         G.clear(); G.resize(n);
         W.clear(); W.resize(n);
         for (int i = , u, v, w; i < n; i++) {
             scanf("%d%d%d", &u, &v, &w);
             G.add(u, v);
             W.add(u, w);
             G.add(v, u);
             W.add(v, w);
         }
         mem0(vis);
         maxd = -;
         DFS();
         int node1 = id;
         mem0(vis);
         maxd = -;
         DFS(id);
         int node2 = id;
         mem0(dis);
         mem0(vis);
         DFS(node1);
         mem0(vis);
         DFS(node2);
         InitRMQ();
         for (int i = , q; i < m; i++) {
             scanf("%d", &q);
             printf("%d\n", solve(q));
         }
     }
     return ;
 }