洛谷 P2147 [SDOI2008]洞穴勘測

P2147 [SDOI2008]洞穴勘測
思路：
按時間分治，而後每條邊有一個存活時間段，按存活時間段將邊加入劃分樹，而後在劃分樹上分治，用可撤銷並查集維護連通性。
代碼：

#pragma GCC optimize(2)
#pragma GCC optimize(3)
#pragma GCC optimize(4)
#include<bits/stdc++.h>
using namespace std;
#define y1 y11
#define fi first
#define se second
#define pi acos(-1.0)
#define LL long long
//#define mp make_pair
#define pb push_back
#define ls rt<<1, l, m
#define rs rt<<1|1, m+1, r
#define ULL unsigned LL
#define pll pair<LL, LL>
#define pli pair<LL, int>
#define pii pair<int, int>
#define piii pair<pii, int>
#define pdd pair<double, double>
#define mem(a, b) memset(a, b, sizeof(a))
#define debug(x) cerr << #x << " = " << x << "\n";
#define fio ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);
//head

const int N = 1e4 + 10, M = 2e5 + 5;
vector<pii> vc[M<<2];
int n, m, u[M], v[M], op[M];
struct UFS {
    stack<pair<int*, int>> stk;
    int fa[N], rnk[N];
    inline void init(int n) {
        for (int i = 0; i <= n; ++i) fa[i] = i, rnk[i] = 0;
    }
    inline int Find(int x) {
        while(x^fa[x]) x = fa[x];
        return x;
    }
    inline void Merge(int x, int y) {
        x = Find(x), y = Find(y);
        if(x == y) return ;
        if(rnk[x] <= rnk[y]) {
            stk.push({fa+x, fa[x]});
            fa[x] = y;
            if(rnk[x] == rnk[y]) {
                stk.push({rnk+y, rnk[y]});
                rnk[y]++;
            }
        }
        else {
            stk.push({fa+y, fa[y]});
            fa[y] = x;
        }
    }
    inline void Undo() {
        *stk.top().fi = stk.top().se;
        stk.pop();
    }
}ufs;
void update(int L, int R, pii p, int rt, int l, int r) {
    if(L <= l && r <= R) return vc[rt].pb(p), void();
    int m = l+r >> 1;
    if(L <= m) update(L, R, p, ls);
    if(R > m) update(L, R, p, rs);
}
void dfs(int rt, int l, int r) {
    for (pii p : vc[rt]) ufs.Merge(p.fi, p.se);
    if(l == r){
        if(op[l] == 2) {
            if(ufs.Find(u[l]) == ufs.Find(v[l])) printf("Yes\n");
            else printf("No\n");
        }
        return ;
    }
    int m = l+r >> 1;
    int sz = ufs.stk.size();
    dfs(ls);
    while(ufs.stk.size() > sz) ufs.Undo();
    dfs(rs);
    while(ufs.stk.size() > sz) ufs.Undo();
}
char s[15];
map<pii, int> mp;
int main() {
    scanf("%d %d", &n, &m);
    ufs.init(n);
    for (int i = 1; i <= m; ++i) {
        scanf("%s", s);
        scanf("%d %d", &u[i], &v[i]);
        if(u[i] > v[i]) swap(u[i], v[i]);
        if(s[0] == 'C') op[i] = 0;
        else if(s[0] == 'D') op[i] = 1;
        else op[i] = 2;
        if(!op[i]) mp[{u[i], v[i]}] = i;
        else if(op[i] == 1) {
            update(mp[{u[i], v[i]}], i-1, {u[i], v[i]}, 1, 1, m);
            mp[{u[i], v[i]}] = 0;
        }
    }

    for (auto it : mp) if(it.se) update(it.se, m, it.fi, 1, 1, m);
    dfs(1, 1, m);
    return 0;
}