題意

給定一個n個節點的樹，每個節點表示一個整數，問u到v的路徑上有多少個不同的整數。
n＝40000，m＝100000

Sol

樹上莫隊模板題

# include <bits/stdc++.h>
# define RG register
# define IL inline
# define Fill(a, b) memset(a, b, sizeof(a))
using namespace std;
const int _(1e5 + 5);
typedef long long ll;

IL int Input(){
    RG int x = 0, z = 1; RG char c = getchar();
    for
 
(; c < '0' || c > '9'; c = getchar()) z = c == '-' ? -1 : 1;
    for(; c >= '0' && c <= '9'; c = getchar()) x = (x << 1) + (x << 3) + (c ^ 48);
    return x * z;
}

int n, m, first[_], cnt, w[_], o[_], len;
int dfn[_], st[20][_], lg[_], deep[_], idx, fa[_];
int
 
 S[_], bl[_], blo, num, ans[_], sum[_], vis[_], Ans;
struct Edge{
    int to, next;
} edge[_];
struct Query{
    int l, r, id;

    IL int operator <(RG Query B) const{
        return bl[l] == bl[B.l] ? dfn[r] < dfn[B.r] : bl[l] < bl[B.l];
    }
} qry[_];

IL void Add(RG int u, RG int v){
    edge[cnt] = (Edge){v, first[u]}, first[u] = cnt++;
}

IL void
 
 Dfs(RG int u){
    dfn[u] = ++idx, st[0][idx] = u; RG int l = S[0];
    for(RG int e = first[u]; e != -1; e = edge[e].next){
        RG int v = edge[e].to;
        if(dfn[v]) continue;
        deep[v] = deep[u] + 1, fa[v] = u;
        Dfs(v);
        if(S[0] - l >= blo) for(++num; S[0] != l; --S[0]) bl[S[S[0]]] = num;
        st[0][++idx] = u;
    }
    S[++S[0]] = u;
}

IL void Chk(RG int &x, RG int u, RG int v){
    x = deep[u] < deep[v] ? u : v;
}

IL int LCA(RG int u, RG int v){
    u = dfn[u], v = dfn[v];
    if(u > v) swap(u, v);
    RG int log2 = lg[v - u + 1], t;
    Chk(t, st[log2][u], st[log2][v - (1 << log2) + 1]);
    return t;
}

IL void Update(RG int x){
    if(vis[x]) --sum[w[x]], Ans -= (!sum[w[x]]);
    else Ans += (!sum[w[x]]), ++sum[w[x]];
    vis[x] ^= 1;
}

IL void Modify(RG int u, RG int v){
    while(u != v){
        if(deep[u] > deep[v]) swap(u, v);
        Update(v), v = fa[v];
    }
}

int main(RG int argc, RG char* argv[]){
    len = n = Input(), m = Input(), blo = sqrt(n);
    for(RG int i = 1; i <= n; ++i) o[i] = w[i] = Input(), first[i] = -1;
    sort(o + 1, o + len + 1), len = unique(o + 1, o + len + 1) - o - 1;
    for(RG int i = 1; i <= n; ++i) w[i] = lower_bound(o + 1, o + len + 1, w[i]) - o;
    for(RG int i = 1, u, v; i < n; ++i)
        u = Input(), v = Input(), Add(u, v), Add(v, u);
    Dfs(1);
    if(S[0]) for(++num; S[0]; --S[0]) bl[S[S[0]]] = num;
    for(RG int i = 2; i <= idx; ++i) lg[i] = lg[i >> 1] + 1;
    for(RG int j = 1; j <= lg[idx]; ++j)
        for(RG int i = 1; i + (1 << j) - 1 <= idx; ++i)
            Chk(st[j][i], st[j - 1][i], st[j - 1][i + (1 << (j - 1))]);
    for(RG int i = 1; i <= m; ++i){
        qry[i] = (Query){Input(), Input(), i};
        if(dfn[qry[i].l] > dfn[qry[i].r]) swap(qry[i].l, qry[i].r);
    }
    sort(qry + 1, qry + m + 1);
    RG int lca = LCA(qry[1].l, qry[1].r);
    Modify(qry[1].l, qry[1].r);
    Update(lca), ans[qry[1].id] = Ans, Update(lca);
    for(RG int i = 2; i <= m; ++i){
        Modify(qry[i - 1].l, qry[i].l), Modify(qry[i - 1].r, qry[i].r);
        lca = LCA(qry[i].l, qry[i].r);
        Update(lca), ans[qry[i].id] = Ans, Update(lca);
    }
    for(RG int i = 1; i <= m; ++i) printf("%d\n", ans[i]);
    return 0;
}

SPOJ：COT2 Count on a tree II