bzoj3757 苹果树

传送门：http://www.lydsy.com/JudgeOnline/problem.php?id=3757

【RE提示】本题不支持提交了，具体可以见discuss，可以通过discuss的方法来做。

【题解】

树上莫队，就是把in/out的DFS序记录下来，每次查找要么查in[a]...in[b],要么查out[a]...in[b]，加上LCA.

然后就正常莫队啦！

# include <math.h>
# include <stdio.h>
# include <string.h>
# include <iostream>
# include <algorithm>
// # include <bits/stdc++.h>

using namespace std;

typedef long long ll;
typedef long double ld;
typedef unsigned long long ull;
const int M = 4e5 + 10;
const int mod = 1e9+7;

# define RG register
# define ST static

int n, m, c[M];
int head[M], nxt[M], to[M], tot = 0;
inline void add(int u, int v) {
    ++tot; nxt[tot] = head[u]; head[u] = tot; to[tot] = v;
}
inline void adde(int u, int v) {
    add(u, v), add(v, u);
}

int fa[M][18], dep[M];
int beg[M], end[M], DFN = 0, dfn[M];
inline void dfs(int x, int fat=0) {
    beg[x] = ++DFN; dfn[DFN] = x;
    fa[x][0] = fat; dep[x] = dep[fat] + 1;
    for (int i=1; i<=17; ++i) fa[x][i] = fa[fa[x][i-1]][i-1];
    for (int i=head[x]; i; i=nxt[i]) 
        if(to[i] != fat) dfs(to[i], x);
    end[x] = ++DFN; dfn[DFN] = x;
}

inline int lca(int u, int v) {
    if(dep[u] < dep[v]) swap(u, v);
    for (int i=17; ~i; --i)
        if((dep[u]-dep[v]) & (1<<i)) u = fa[u][i];
    if(u == v) return u;
    for (int i=17; ~i; --i)
        if(fa[u][i] != fa[v][i]) u = fa[u][i], v = fa[v][i];
    return fa[u][0];
}

int bl[M], BLOCK;
struct pa {
    int u, v, a, b, p, id;
    pa() {}
    pa(int u, int v, int a, int b, int p, int id) : u(u), v(v), a(a), b(b), p(p), id(id) {}
    friend bool operator < (pa a, pa b) {
        return bl[a.u] < bl[b.u] || (bl[a.u] == bl[b.u] && bl[a.v] < bl[b.v]);
    }
}p[M];

int ans[M];
int t[M], s[M], cnt;
inline void doit(int x) {
    t[x] ++;
    if(t[x] == 1) {
        ++s[c[x]];
        if(s[c[x]] == 1) ++cnt;
    } else {
        --s[c[x]];
        if(s[c[x]] == 0) --cnt;
    }
    if(t[x] == 2) t[x] = 0;
}

int main() {
    cin >> n >> m;
    for (int i=1; i<=n; ++i) scanf("%d", &c[i]);
    for (int i=1, u, v; i<=n; ++i) {
        scanf("%d%d", &u, &v);
        if(u && v) adde(u, v);
    }
    dfs(1);
    BLOCK = sqrt(n);
    for (int i=1; i<=DFN; ++i) bl[i] = (i-1)/BLOCK+1;
    for (int i=1, u, v, a, b; i<=m; ++i) {
        scanf("%d%d%d%d", &u, &v, &a, &b);
        int LCA = lca(u, v);
        if(beg[u] > beg[v]) swap(u, v);
        if(LCA == u) p[i] = pa(beg[u], beg[v], a, b, 0, i);
        else p[i] = pa(end[u], beg[v], a, b, LCA, i);
    }
    sort(p+1, p+m+1);
    int L = 1, R = 0;
    for (int i=1; i<=m; ++i) {
        while(R < p[i].v) ++R, doit(dfn[R]);
        while(R > p[i].v) doit(dfn[R]), --R;
        while(L > p[i].u) --L, doit(dfn[L]);
        while(L < p[i].u) doit(dfn[L]), ++L;
        if(p[i].p) doit(p[i].p);
        if(p[i].a == p[i].b) ans[p[i].id] = cnt;
        else {
            if(s[p[i].a] && s[p[i].b]) ans[p[i].id] = cnt-1;
            else ans[p[i].id] = cnt;
        }
        if(p[i].p) doit(p[i].p);
    }
    for (int i=1; i<=m; ++i) printf("%d
", ans[i]);
    return 0;
}