二分图排列

#include<bits/stdc++.h>
using namespace std;

const int N=1e6+5,inf=1e9;

int n;
int a[N],f[N][2];
vector <int> p;

inline void solve(){
	scanf("%d",&n);
	for(int i=1;i<=n;++i) scanf("%d",&a[i]);
	for(int i=0;i<=n;++i) f[i][0]=f[i][1]=-inf;
	f[n][0]=f[n][1]=inf;
	for(int i=n-1;i;--i){
		int t0[4]={-a[i+1],a[i+1],f[i+1][0],f[i+1][1]};
		int t1[4]={f[i+1][0],f[i+1][1],-a[i+1],a[i+1]};
		for(int j=0;j<2;++j){
			int t=(!j)?-a[i]:a[i];
			for(int k=0;k<4;++k)
				if(t<t0[k])
					f[i][j]=max(f[i][j],t1[k]);
		}
		if(f[i][0]==-inf&&f[i][1]==-inf){
			puts("NO");
			return;
		}
	}
	puts("YES");
	int t1=f[0][0],t2=f[0][0];
	for(int i=1;i<=n;++i){
		if(-a[i]>t1)
			t1=a[i]=-a[i];
		else if(-a[i]>t2&&-a[i]<f[i][0])
			t2=a[i]=-a[i];
		else t1=a[i];
		if(t1<t2) swap(t1,t2);
		printf("%d ",a[i]);
	}
	puts("");
}

signed main(){
#ifndef ONLINE_JUDGE
	freopen("1.in","r",stdin);
	freopen("1.out","w",stdout);
#endif
	int T;
	scanf("%d",&T);
	while(T--) solve();
	return 0;
}
/*
4
3
1 2 3
6
1 3 2 6 5 4
4
4 1 3 2
8
3 2 1 6 7 8 5 4
*/

搬题能不能搬简单点啊！

最短路问题 V3

#include<bits/stdc++.h>
using namespace std;

using ll=long long;
#define emp emplace_back
#define int long long
const ll inf=1e15;
const int N=2e5+100;

struct E{
	int x,w;
	E(int a,int b){x=a,w=b;}
};

int n,m;
ll d[85][N];
int f[N][20],dep[N],ds[N];
vector <E> G[N];
vector <int> p;
bool vis[N];

inline void spfa(int s){
	queue <int> q;
	for(int i=1;i<=n;++i) d[s][i]=inf;
	d[s][p[s]]=0;
	q.push(p[s]);
	memset(vis,0,sizeof(vis));
	vis[p[s]]=1;
	while(!q.empty()){
		int x=q.front();
		q.pop();
		vis[x]=0;
		for(auto y:G[x]){
			if(d[s][y.x]>d[s][x]+y.w){
				d[s][y.x]=d[s][x]+y.w;
				if(!vis[y.x]) vis[y.x]=1,q.push(y.x);
			}
		}
	}
}
inline void dfs(int x,int fa){
	f[x][0]=fa;
	for(int i=1;i<=19;++i)
		f[x][i]=f[f[x][i-1]][i-1];
	for(auto y:G[x]){
		if(y.x==fa) continue;
		if(f[y.x][0]==0){
			dep[y.x]=dep[x]+1;
			ds[y.x]=ds[x]+y.w;
			dfs(y.x,x);
		}
		else if(dep[x]<dep[y.x]){
			p.emp(x);
			spfa(p.size()-1);
			p.emp(y.x);
			spfa(p.size()-1);
		}
	}
}
inline int lca(int x,int y){
	if(dep[x]<dep[y])
		swap(x,y);
	for(int i=19;i>=0;--i)
		if(dep[f[x][i]]>=dep[y])
			x=f[x][i];
	if(x==y) return x;
	for(int i=19;i>=0;--i)
		if(f[x][i]!=f[y][i])
			x=f[x][i],y=f[y][i];
	return f[x][0];
}
signed main(){
#ifndef ONLINE_JUDGE
	freopen("1.in","r",stdin);
	freopen("2.out","w",stdout);
#endif
	int q;
	scanf("%lld%lld",&n,&m);
	for(int i=1;i<=m;++i){
		int x,y,z;
		scanf("%lld%lld%lld",&x,&y,&z);
		//cout<<x<<" "<<y<<" "<<z<<endl;
		G[x].emp(y,z);G[y].emp(x,z);
	}
	dfs(1,1);
	scanf("%lld",&q);
	for(int i=1;i<=q;++i){
		int x,y;
		scanf("%lld%lld",&x,&y);
		bool fl=0;
		int z=ds[x]+ds[y]-2*ds[lca(x,y)];
		for(int i=0;i<(int)p.size();++i)
			z=min(z,d[i][x]+d[i][y]);
		printf("%lld\n",z);
	}
	return 0;
}

捡石子游戏

我写的记搜，复杂度 \(\rm O(n)\)。

#include<bits/stdc++.h>
using namespace std;

const int N=3e3+5;

#define emp emplace_back

int n;
int f[N],a[N];
vector <int> p,G[N];

inline int dfs(int x){
	if(f[x]!=-1) return f[x];
	f[x]=0;
	for(int y:G[x])
		if(a[y]<a[x])
			f[x]|=(dfs(y)^1);
	return f[x];
}

signed main(){
#ifndef ONLINE_JUDGE
	freopen("1.in","r",stdin);
	freopen("2.out","w",stdout);
#endif
	scanf("%d",&n);
	memset(f,-1,sizeof(f));
	for(int i=1;i<=n;++i){
		scanf("%d",&a[i]);
	}
	for(int i=1,x,y;i<n;++i){
		scanf("%d%d",&x,&y);
		G[x].emp(y),G[y].emp(x);
	}
	for(int i=1;i<=n;++i)
		if(dfs(i)) p.emp(i);
	if(!p.size()) puts("-1");
	else for(int x:p) printf("%d ",x);
	return 0;
}