[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[8] = {1, 0, -1, 0, 1, 1, -1, -1};
const int dy[8] = {0, -1, 0, 1, -1, 1, 1, -1};
const int maxn = 1e5 + 7;
const int maxm = 1e5 + 7;
const int maxv = 1e7 + 7;
const int MD = 1e9 +7;
const int INF = 1e9 + 7;
const double PI = acos(-1.0);
const double eps = 1e-10;

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() < 2) return T(); return *(Q.end() - 2); }
    T front() { return Q.front(); }
};

template<class edge> struct Graph {
    vector<vector<edge> > adj;
    Graph(int n) { adj.clear(); adj.resize(n + 5); }
    Graph() { adj.clear(); }
    void resize(int n) { adj.resize(n + 5); }
    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][20], minf[maxn][20];
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 = 0; 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 = 1; i <= n; i++) maxf[i][0] = minf[i][0] = dis[i];
    for (int j = 1; (1 << j) <= n; j++) {
        for (int i = 1; i + (1 << j) - 1 <= n; i++) {
            maxf[i][j] = max(maxf[i][j - 1], maxf[i + (1 << (j - 1))][j - 1]);
            minf[i][j] = min(minf[i][j - 1], minf[i + (1 << (j - 1))][j - 1]);
        }
    }
}
int RMQ_max(int L, int R) {
    int x = t[R - L + 1];
    return max(maxf[L][x], maxf[R - (1 << x) + 1][x]);
}
int RMQ_min(int L, int R) {
    int x = t[R - L + 1];
    return min(minf[L][x], minf[R - (1 << x) + 1][x]);
}

int solve(int q) {
    int L = 1, ans = 0;
    for (int R = 1; R <= n; R++) {
        while (RMQ_max(L, R) - RMQ_min(L, R) > q) L++;
        ans = max(ans, R - L + 1);
    }
    return ans;
}

int main() {
    //freopen("in.txt", "r", stdin);
    for (int i = 1; i <= 50000; i++) {
        int j = 0;
        while ((1 << (j + 1)) <= i) j++;
        t[i] = j;
    }
    while (cin >> n >> m, n || m) {
        G.clear(); G.resize(n);
        W.clear(); W.resize(n);
        for (int i = 1, 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 = -1;
        DFS(1);
        int node1 = id;
        mem0(vis);
        maxd = -1;
        DFS(id);
        int node2 = id;
        mem0(dis);
        mem0(vis);
        DFS(node1);
        mem0(vis);
        DFS(node2);
        InitRMQ();
        for (int i = 0, q; i < m; i++) {
            scanf("%d", &q);
            printf("%d
", solve(q));
        }
    }
    return 0;
}