【LOJ】#2062. 「HAOI2016」地图

题解

我对莫队真是一无所知

这个东西显然可以用圆方树转成一个dfs序列

然后呢，用莫队计算每个询问区间的每个数出现的次数，从而顺带计算每个数字的奇偶性

但是我们要查的数字也用一个范围，可以直接用分块维护，修改\(O(1)\)查询\(O(n)\)

代码

#include <bits/stdc++.h>
#define enter putchar('\n')
#define space putchar(' ')
#define pii pair<int,int>
#define fi first
#define se second
#define MAXN 200005
#define pb push_back
#define mp make_pair
//#define ivorysi
using namespace std;
typedef long long int64;
typedef double db;
template<class T>
void read(T &res) {
    res = 0;T f = 1;char c = getchar();
    while(c < '0' || c > '9') {
        if(c == '-') f = -1;
        c = getchar();
    }
    while(c >= '0' && c <= '9') {
        res = res * 10 + c - '0';
        c = getchar();
    }
}
template<class T>
void out(T x) {
    if(x < 0) {x = -x;putchar('-');}
    if(x >= 10) out(x / 10);
    putchar('0' + x % 10);
}
struct qry_node {
    int l,r,bl,v,y,id;
    friend bool operator < (const qry_node &a,const qry_node &b) {
        if(a.bl != b.bl) return a.bl < b.bl;
        if(a.r != b.r) return a.r < b.r;
        if(a.l != b.l) return a.l < b.l;
        return a.id < b.id;
    }
}qry[MAXN];
struct node {
    int to,next;
}E[MAXN * 2];
int N,M,Q;
int head[MAXN],sumE;
int siz[MAXN],L[MAXN],a[MAXN],num[MAXN],cnt,S[350][2],bl[MAXN],br[MAXN],id[MAXN],tot;
int tims[MAXN],st,ed,ans[MAXN];
vector<int> ver[MAXN];
int sta[MAXN],top,dfn[MAXN],low[MAXN],idx;
void add(int u,int v) {
    E[++sumE].to = v;
    E[sumE].next = head[u];
    head[u] = sumE;
}
void Tarjan(int u) {
    dfn[u] = low[u] = ++idx;
    sta[++top] = u;
    for(int i = head[u] ; i ; i = E[i].next) {
        int v = E[i].to;
        if(dfn[v]) low[u] = min(low[u],dfn[v]);
        else {
            Tarjan(v);
            if(low[v] >= dfn[u]) {
                while(1) {
                    int x = sta[top--];
                    ver[u].pb(x);
                    if(x == v) break;
                }
            }
            else low[u] = min(low[u],low[v]);
        }
    }
}
void dfs(int u) {
    int s = ver[u].size();
    dfn[u] = ++idx;siz[u] = 1;L[idx] = a[u];
    for(int i = 0 ; i < s ; ++i) {
        dfs(ver[u][i]);
        siz[u] += siz[ver[u][i]];
    }
}
void Init() {
    read(N);read(M);
    for(int i = 1 ; i <= N ; ++i) {read(a[i]);num[i] = a[i];}
    sort(num + 1,num + N + 1);
    cnt = unique(num + 1,num + N + 1) - num - 1;
    for(int i = 1 ; i <= N ; ++i) a[i] = lower_bound(num + 1,num + cnt + 1,a[i]) - num;
    int u,v;
    for(int i = 1 ; i <= M ; ++i) {
        read(u);read(v);add(u,v);add(v,u);
    }
    Tarjan(1);
    idx = 0;
    dfs(1);
    int s = sqrt(cnt);
    for(int i = 1 ; i <= cnt ; i += s) {
        bl[++tot] = i,br[tot] = min(cnt,i + s - 1);
    }
    for(int i = 1 ; i <= tot ; ++i) {
        for(int j = bl[i] ; j <= br[i] ; ++j) {
            id[j] = i;
        }
    }
    s = sqrt(N);
    read(Q);
    for(int i = 1 ; i <= Q ; ++i) {
        read(qry[i].v);read(u);read(qry[i].y);
        qry[i].id = i;qry[i].l = dfn[u];qry[i].r = dfn[u] + siz[u] - 1;
        qry[i].bl = qry[i].l / s + 1;
    }
    sort(qry + 1,qry + Q + 1);
}
void Insert(int p) {
    if(tims[p]) S[id[p]][tims[p] & 1]--;
    ++tims[p];
    S[id[p]][tims[p] & 1]++;
}
void Erase(int p) {
    S[id[p]][tims[p] & 1]--;
    --tims[p];
    if(tims[p]) S[id[p]][tims[p] & 1]++;
}
void Move(int l,int r) {
    while(ed < r) {Insert(L[++ed]);}
    while(st > l) {Insert(L[--st]);}
    while(ed > r) {Erase(L[ed--]);}
    while(st < l) {Erase(L[st++]);}
}
void Solve() {
    st = 1,ed = 0;
    for(int i = 1 ; i <= Q ; ++i) {
        Move(qry[i].l,qry[i].r);
        int res = 0;
        int t;
        if(qry[i].y >= num[cnt]) t = cnt;
        else t = upper_bound(num + 1,num + cnt + 1,qry[i].y) - num - 1;
        for(int j = 1 ; j <= id[t] - 1 ; ++j) {
            res += S[j][qry[i].v];
        }
        for(int j = bl[id[t]] ; j <= t ; ++j) {
            if(!tims[j]) continue;
            res += ((tims[j] & 1) == qry[i].v);
        }
        ans[qry[i].id] = res;
    }
    for(int i = 1 ; i <= Q ; ++i) {
        out(ans[i]);enter;
    }
}
int main() {
#ifdef ivorysi
    freopen("f1.in","r",stdin);
#endif
    Init();
    Solve();
    return 0;
}