HDU4358【离散化+DFS序+莫队算法】

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思路：
这个DFS序还是蛮有意思的~然后就可以把以u为根的树的状态直接转化到区间（一维数组）上，而且数组是不大的。
然后就变成了区间处理，套一下莫队就好了。
Code:

#include<bits/stdc++.h>using namespace std;typedef long long LL;#define mem(a, b) memset(a, b, sizeof(a))const int Maxn = 1e5 + 10;struct Edge{int v, nex;}edge[Maxn<<1];int head[Maxn], tol;void init(){tol = 0,mem(head, -1);}void addedge(int u, int v){    edge[tol] = (Edge){v, head[u]}, head[u] = tol++;    edge[tol] = (Edge){u, head[v]}, head[v] = tol++;}int w[Maxn], _time, val[Maxn], n, k, q, a[Maxn];int Left[Maxn], Right[Maxn];vector<int>xs;struct asd{    int id;    int Left, Right;}node[Maxn];int res[Maxn], ans, sum[Maxn];int pos[Maxn];bool cmp(asd x,asd y){    if(pos[x.Left] == pos[y.Left])        return x.Right<y.Right;    return pos[x.Left]<pos[y.Left];}void DFS(int u, int fa){    int v;    Left[u] = ++_time, w[_time] = a[u];    for(int i=head[u]; ~i;i = edge[i].nex){        v = edge[i].v;        if(v == fa) continue;        DFS(v, u);    }    Right[u] = _time;}void ADD(int ww){    if(sum[ww] == k) ans--;    sum[ww]++;    if(sum[ww] == k) ans++;}void DEL(int ww){    if(sum[ww] == k) ans--;    sum[ww]--;    if(sum[ww] == k) ans++;}void solve(){    ans=0;    mem(sum, 0);    sort(node+1, node+1+q, cmp);    for(int i=node[1].Left;i<=node[1].Right;i++){        ADD(w[i]);    }    res[node[1].id]=ans;    int L=node[1].Left,R=node[1].Right;    for(int i=2; i<=q; i++){        while(R<node[i].Right){            R++;            ADD(w[R]);        }        while(R>node[i].Right){            DEL(w[R]);            R--;        }        while(L<node[i].Left){            DEL(w[L]);            L++;        }        while(L>node[i].Left){            L--;            ADD(w[L]);        }        res[node[i].id]=ans;    }    for(int i=1;i<=q;i++)        printf("%d\n", res[i]);}int main(){    int T, u, v, L, R;    scanf("%d", &T);    for(int cas = 1; cas <= T; cas++){        scanf("%d%d",&n, &k);        xs.clear();        int block=(int)sqrt(n);        for(int i=1;i<=n;i++){            scanf("%d", &a[i]);            xs.push_back(a[i]);            pos[i]=(i-1)/block+1;        }        sort(xs.begin(), xs.end());        xs.erase(unique(xs.begin(), xs.end()), xs.end());        for(int i=1;i<=n;++i) a[i] = lower_bound(xs.begin(), xs.end(), a[i]) - xs.begin() + 1;        init();        for(int i=1;i<n;i++){            scanf("%d%d", &u, &v);            addedge(u, v);        }        _time = 0;        DFS(1, -1);        scanf("%d", &q);        for(int i=1;i<=q;i++){            scanf("%d", &u);            node[i].id = i;            node[i].Left = Left[u], node[i].Right = Right[u];        }        printf("Case #%d:\n", cas);        solve();        if(cas != T) puts("");    }    return 0;}

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