题目链接:点击打开链接
题意:
给定n个点 m条边的无向图 须要在图里添加p条边 使得图最后连通分量数为q
问是否可行,不可行输出NO
可行输出YES,并输出加入的p条边。
set走起。。
#include<stdio.h> #include<iostream> #include<string.h> #include<algorithm> #include<vector> #include<set> using namespace std; #define N 123456 #define ll __int64 ll n,m,p,q; struct Edge{ ll from, to, dis; }edge[N*2]; ll edgenum; void add(ll u,ll v,ll dis){ Edge E={u,v,dis}; edge[edgenum++] = E; } ll f[N]; ll find(ll x){return x==f[x]?x:f[x]=find(f[x]);} void Union(ll x,ll y){ ll fx = find(x), fy = find(y); if(fx==fy)return ; if(fx<fy)swap(fx,fy); f[fx]=fy; } set<ll>myset; set<ll>::iterator pp; ll siz[N]; vector<int>L,R; struct node{ ll fa, val; bool operator<(const node&x)const{ if(x.val==val)return x.fa<fa; return x.val>val; } node(ll x=0,ll y = 0):fa(x),val(y){} }; set<node>hehe; set<node>::iterator dd; void init(){ hehe.clear(); L.clear(); R.clear(); memset(siz, 0, sizeof siz); myset.clear(); for(ll i = 1; i <= n; i++)f[i]=i; edgenum = 0; } void go(){ dd = hehe.begin(); node x = *dd; hehe.erase(dd); dd = hehe.begin(); node y = *dd; hehe.erase(dd); Union(x.fa,y.fa); ll now = min((ll)1000000000, x.val+y.val+1); node z = node(find(x.fa),x.val+y.val+now); hehe.insert(z); L.push_back(x.fa); R.push_back(y.fa); add(x.fa,y.fa,1); } int main(){ ll i, j, u, v, d; while(~scanf("%I64d %I64d %I64d %I64d",&n,&m,&p,&q)){ init(); while(m--){ scanf("%I64d %I64d %I64d",&u,&v,&d); add(u,v,d); Union(u,v); } for(i = 1; i <= n; i++)find(i); for(i = 1; i <= n; i++)myset.insert(f[i]); for(i = 0; i < edgenum; i++){ siz[f[edge[i].from]]+=edge[i].dis; } if(myset.size()<q){puts("NO");continue;} if(myset.size()==q) { if(p && edgenum==0)puts("NO"); else { puts("YES"); while(p--){ cout<<edge[0].from<<" "<<edge[0].to<<endl; } } continue; } ll ned = myset.size()-q; if(ned>p){puts("NO");continue;} p-=ned; for(pp=myset.begin(); pp!=myset.end(); pp++)hehe.insert(node(*pp,siz[*pp])); while(ned--)go(); puts("YES"); for(i = 0; i < L.size(); i++)cout<<L[i]<<" "<<R[i]<<endl; while(p--) cout<<edge[0].from<<" "<<edge[0].to<<endl; } return 0; }
时间: 2024-10-14 14:09:56