CF1278D Segment Tree(set+並查集)
阿新 • • 發佈:2021-08-04
// Problem: CF1278D Segment Tree // Contest: Luogu // URL: https://www.luogu.com.cn/problem/CF1278D // Memory Limit: 250 MB // Time Limit: 2000 ms // Author:Cutele // // Powered by CP Editor (https://cpeditor.org) #include<bits/stdc++.h> using namespace std; typedef long long ll; typedef unsigned long long ull; typedef pair<ll, ll>PLL; typedef pair<int, int>PII; typedef pair<double, double>PDD; #define I_int ll inline ll read() { ll x = 0, f = 1; char ch = getchar(); while(ch < '0' || ch > '9') { if(ch == '-')f = -1; ch = getchar(); } while(ch >= '0' && ch <= '9') { x = x * 10 + ch - '0'; ch = getchar(); } return x * f; } inline void out(ll x){ if (x < 0) x = ~x + 1, putchar('-'); if (x > 9) out(x / 10); putchar(x % 10 + '0'); } inline void write(ll x){ if (x < 0) x = ~x + 1, putchar('-'); if (x > 9) write(x / 10); putchar(x % 10 + '0'); } #define read read() #define closeSync ios::sync_with_stdio(0);cin.tie(0);cout.tie(0) #define multiCase int T;cin>>T;for(int t=1;t<=T;t++) #define rep(i,a,b) for(int i=(a);i<=(b);i++) #define repp(i,a,b) for(int i=(a);i<(b);i++) #define per(i,a,b) for(int i=(a);i>=(b);i--) #define perr(i,a,b) for(int i=(a);i>(b);i--) ll ksm(ll a, ll b,ll p) { ll res = 1; while(b) { if(b & 1)res = res * a%p; a = a * a %p; b >>= 1; } return res; } const int inf = 0x3f3f3f3f; const int maxn=5e5+7; int root[maxn]; struct node{ int l,r; bool operator < (const node & A) const{ return l < A.l; } }a[maxn]; int Find(int x){ if(x!=root[x]) root[x]=Find(root[x]); return root[x]; } set<node>s; int main(){ int n=read; rep(i,1,n){ a[i].l=read,a[i].r=read;root[i]=i; } sort(a+1,a+n+1); s.insert({a[1].r,1}); rep(i,2,n){ while(s.size()){ node t=*s.begin(); if(t.l<=a[i].l) s.erase(s.begin()); else break; } for(set<node>::iterator it=s.begin();it!=s.end();it++){ node t=*it; if(t.l<a[i].r){ int u=i,v=t.r; int fu=Find(u),fv=Find(v); if(fu!=fv) root[fu]=fv; else{ puts("NO");return 0; } } else break; } s.insert({a[i].r,i}); } int res=0; for(int i=1;i<=n;i++) if(i==Find(i)) res++; if(res==1) puts("YES"); else puts("NO"); return 0; }