Bipartite Checking CodeForces - 813F (线段树按时间分治)

大意: 动态添边, 询问是否是二分图.

算是个线段树按时间分治入门题, 并查集维护每个点到根的奇偶性即可.

#include <iostream>

#include <sstream>

#include <algorithm>

#include <cstdio>

#include <cmath>

#include <set>

#include <map>

#include <queue>

#include <string>

#include <cstring>

#include <bitset>

#include <functional>

#include <random>

#define REP(i,a,n) for(int i=a;i<=n;++i)

#define PER(i,a,n) for(int i=n;i>=a;--i)

#define hr putchar(10)

#define pb push_back

#define lc (o<<1)

#define rc (lc|1)

#define mid ((l+r)>>1)

#define ls lc,l,mid

#define rs rc,mid+1,r

#define x first

#define y second

#define io std::ios::sync_with_stdio(false)

#define endl '\n'

#define DB(a) ({REP(__i,1,n) cout<<a[__i]<<',';hr;})

using namespace std;

typedef long long ll;

typedef pair<int,int> pii;

const int P = 1e9+7, INF = 0x3f3f3f3f;

ll gcd(ll a,ll b) {return b?gcd(b,a%b):a;}

ll qpow(ll a,ll n) {ll r=1%P;for (a%=P;n;a=a*a%P,n>>=1)if(n&1)r=r*a%P;return r;}

ll inv(ll x){return x<=1?1:inv(P%x)*(P-P/x)%P;}

inline int rd() {int x=0;char p=getchar();while(p<'0'||p>'9')p=getchar();while(p>='0'&&p<='9')x=x*10+p-'0',p=getchar();return x;}

//head

const int N = 1e6+50;

int n, q, fa[N], sz[N], dis[N];

map<pii,vector<int> > g;

vector<pii> tr[N<<2];

void add(int o, int l, int r, int ql, int qr, pii v) {

	if (ql<=l&&r<=qr) return tr[o].pb(v);

	if (mid>=ql) add(ls,ql,qr,v);

	if (mid<qr) add(rs,ql,qr,v);

}

int Find(int x) {while (fa[x]!=x) x=fa[x];return x;}

vector<pair<int*,int> > tag[30];

void build(int o, int l, int r, int d) {

	tag[d].clear();

	for (auto &t:tr[o]) {

		int z = 1, x = t.x, y = t.y;

		while (fa[x]!=x) z^=dis[x],x=fa[x];

		while (fa[y]!=y) z^=dis[y],y=fa[y];

		if (x==y) {

			if (z&1) {

				REP(i,l,r) puts("NO");

				for (auto &t:tag[d]) *t.x=t.y;

				return;

			}

		}

		if (sz[x]<sz[y]) swap(x,y);

		tag[d].pb({&sz[x],sz[x]});

		tag[d].pb({&fa[y],fa[y]});

		tag[d].pb({&dis[y],dis[y]});

		sz[x] += sz[y];

		fa[y] = x, dis[y] = z;

	}

	if (l==r) puts("YES");

	else build(ls,d+1),build(rs,d+1);

	for (auto &t:tag[d]) *t.x = t.y;

}

int main() {

	scanf("%d%d", &n, &q);

	REP(i,1,q) {

		int u ,v;

		scanf("%d%d", &u, &v);

		g[pii(u,v)].pb(i);

	}

	for (auto &t:g) {

		for (int i=0; i<t.y.size(); ++i) {

			if (i+1==t.y.size()) add(1,1,q,t.y[i],q,t.x);

			else {

				add(1,1,q,t.y[i],t.y[i+1]-1,t.x);

				++i;

			}

		}

	}

	REP(i,1,n) fa[i] = i, sz[i] = 1;

	build(1,1,q,0);

}