Submission #982422

#	Time	Username	Problem	Language	Result	Execution time	Memory
982422		Lib	Swapping Cities (APIO20_swap)	C++14	100 / 100	365 ms	71324 KiB

swap

#include <bits/stdc++.h>
using namespace std;
int n,m,a,b,c;
vector <vector <int> > InComponents;
vector <vector <int> > adj; //the edge list of the KRT
vector <int> TVector;
int RootID; //ID of the root node of the KRT;
struct Edge{
	long long Weight;
	int Start;
	int End;
};
bool operator< (const Edge &x, const Edge &y){
	return x.Weight<y.Weight;
}
Edge Elist[500003];
int Depth[500003];
int Deg[500003];
int CurRep[500003]; //id of the respresentative node on the KRT
int Par[500003]; //Parent of node with id i on the KRT;
int Toggle[500003]; //is the i-th node on the KRT toggled?
int Check[500003];
int Ancestor[500003][25];
int Val[500003];//the value of the i-th node of the KRT
vector <int> KRTID;
int GetRep(int u){
	if(CurRep[u]==-1){
		return u;
	}else{
		return CurRep[u]=GetRep(CurRep[u]);
	}
}
void DSU(int id, int u, int v, int w){
	int CurID=n-1+id;
	Deg[u]++;
	Deg[v]++;
	//u and v belongs to the same component. The component now has a cycle. Immediately toggle the root node of the current 
	//subtree that includes both u and v on the KRT
	//Screw partial, binary tree KRT, opt into full-KRT instead
	int RepU=GetRep(u), RepV=GetRep(v);
	if(RepU==RepV){
		Par[RepU]=CurID;
		Val[CurID]=w;
		adj[RepU].push_back(CurID);
		adj[CurID].push_back(RepU);
		CurRep[RepU]=CurID;
		//The node isn't toggled just yet. Toggle it immediately as there is a cycle
		Toggle[CurID]=1;
	}else{
		//u and v doesn't belong to the same component. Merge them
		int OldComp1=RepU, OldComp2=RepV;
		adj[RepU].push_back(CurID);
		adj[RepV].push_back(CurID);
		adj[CurID].push_back(RepU);
		adj[CurID].push_back(RepV);
		Par[RepU]=CurID;
		Par[RepV]=CurID;
		CurRep[RepU]=CurID;
		CurRep[RepV]=CurID;
		Val[CurID]=w; //if I got WA because I forgot to set the fucking node weight to the nodes on the KRT, I'll shove 3 fingers up my ass.
		//if either of the components are toggled already (having a cycle OR a vertex with degree >=3)
		//OR the merged component has a vertex with degree >3 (either u or v), toggle immediately
		if(Toggle[OldComp1]||Toggle[OldComp2]||Deg[u]>2||Deg[v]>2){
			Toggle[CurID]=1;
		}
	}
	//cout<<CurID<<" ";
}
void init(int N, int M, vector <int> U, vector <int> V, vector <int> W){
	n=N;
	m=M;
	for(int i=0;i<n+m+5;i++){
		adj.push_back(TVector);
	}
	for(int i=1;i<=m;i++){
		Elist[i].Weight=W[i-1];
		Elist[i].Start=U[i-1];
		Elist[i].End=V[i-1];
	}
	sort(Elist+1,Elist+m+1);
	for(int i=0;i<=m+n+1;i++){
		CurRep[i]=-1;
		Par[i]=-1;
		Toggle[i]=0;
	}		
	for(int i=1;i<=m;i++){
		DSU(i,Elist[i].Start,Elist[i].End,Elist[i].Weight);
	}
	//The KRT is now built. BFS from the root node and initialize LCA or something
	deque <int> dq;
	RootID=n+m-1;
	dq.push_back(RootID);
	Check[RootID]=1;
	int Cur;
	while(!dq.empty()){
		Cur=dq.front();
		for(int i=0;i<adj[Cur].size();i++){
			if(!Check[adj[Cur][i]]){
				dq.push_back(adj[Cur][i]);
				Check[adj[Cur][i]]=1;
				Depth[adj[Cur][i]]=Depth[Cur]+1;
			}
		}
		dq.pop_front();
	}
	for(int i=0;i<=20;i++){
		for(int k=0;k<n+m;k++){
			if(i==0){
				Ancestor[k][0]=Par[k];
			}else{
				if(Depth[k]<pow(2,i)){
					Ancestor[k][i]=-1;
				}else{
				Ancestor[k][i]=Ancestor[Ancestor[k][i-1]][i-1];
				}
			}
		}
	}
}
int getMinimumFuelCapacity(int x, int y){
	//I thought that we actually need to use binary lifting to find LCA and then jump from the LCA to find the nearest
	//toggled node on the KRT
	//But apparently small-to-large merging ensures that the depth of the tree is always logN or something, so bruteforcing
	//it is
	//ok nvm this guy is a fucking moron lmao LogN depth my ass. Wrong analysis, wasted 5 minutes. Fuck me
	if(!Toggle[RootID]){
		return -1;
	}
	if(Depth[x]<Depth[y]){
		swap(x,y);
	}

	int JumpLevel=Depth[x]-Depth[y];
	for(int i=19;i>=0;i--){
		if(JumpLevel >> i & 1){
			x=Ancestor[x][i];
		}
	}
	for(int i=20;i>=0;i--){
		if(Ancestor[x][i]!=Ancestor[y][i]){
			x=Ancestor[x][i];
			y=Ancestor[y][i];
		}
	}
	x=Par[x];
	y=Par[y];
	if(Toggle[x]){
		return Val[x];
	}
	for(int i=20;i>=0;i--){
		if(Ancestor[x][i]!=-1&&!Toggle[Ancestor[x][i]]){
			x=Ancestor[x][i];
		}
	}
	x=Par[x];
	if(Toggle[x]&&x!=-1){
		return Val[x];
	}
}
/*
Post-AC comments:
- In a classic me fashion, did pretty much everything right, built the KRT which is relatively complicated bullshit (not really but well) and all, but then
......fucks up BINARY LIFTING. Yep, classic me.
- Use a Full-KRT instead of a Binary-KRT (i.e: when the DSU adds an edge that connects between 2 vertex that is currently in the same connected components,
instead of discarding that edge completely, still add it into the KRT instead). Less casework and headache - inducing bugs that way.
- This is literally the first time I've touched DSU since...May last year (that's why the first few submissions are utter fucking dogshit with some shitass bruteforce
union merging that doesn't even work), also the first time I implemented the KRT as well. Fun stuffs,
*/

//IO for later uses
/*
int q;
int main(){
	ios_base::sync_with_stdio(false);
	cin.tie(NULL);
	cout.tie(NULL);
	freopen("swap_12_2.in","r",stdin);
	cin>>n>>m;
	vector <int> U,V,W;
	for(int i=1;i<=m;i++){
		cin>>a>>b>>c;
		U.push_back(a);
		V.push_back(b);
		W.push_back(c);
	}
	init(n,m,U,V,W);
	deque <int> dq;
	cin>>q;
	for(int i=1;i<=q;i++){
		cin>>a>>b;
		dq.push_back(getMinimumFuelCapacity(a,b));
		cout<<dq.back()<<"\n";
	}
	freopen("swap_12_2.out","r",stdin);
	int cur, score=0;
	for(int i=1;i<=q;i++){
		cin>>cur;
		if(cur==dq.front()){
			score++;
		}else{
			cout<<dq.front()<<" "<<cur<<" "<<Val[RootID]<<"\n";
		}
		dq.pop_front();
	}
	cout<<score<<" "<<q<<" ";
	int maxdepth=0;
	for(int i=0;i<=n+m+5;i++){
		maxdepth=max(maxdepth,Depth[i]);
	}
	//cout<<maxdepth;
}
*/

Compilation message (stderr)

swap.cpp: In function 'void init(int, int, std::vector<int>, std::vector<int>, std::vector<int>)':
swap.cpp:97:16: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   97 |   for(int i=0;i<adj[Cur].size();i++){
      |               ~^~~~~~~~~~~~~~~~
swap.cpp: In function 'int getMinimumFuelCapacity(int, int)':
swap.cpp:159:1: warning: control reaches end of non-void function [-Wreturn-type]
  159 | }
      | ^

• Subtask 1: 6 / 6
• Subtask 2: 7 / 7
• Subtask 3: 17 / 17
• Subtask 4: 20 / 20
• Subtask 5: 23 / 23
• Subtask 6: 27 / 27