delete pics to save space

1.1967.cpp

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+#include<cstdio>
+#include<cstring>
+#include<vector>
+#include<algorithm>
+using namespace std;
+const int maxn=10005;
+const int maxm=50005;
+const int oo=0x3f3f3f3f;
+struct Edge { int v,w; Edge *next; };
+Edge mem[maxm*2],*G[maxn],*ecnt=mem;
+inline void AddEdge(int u,int v,int w) { ecnt->v=v; ecnt->w=w; ecnt->next=G[u]; G[u]=ecnt++; } 
+int n,m,q;
+namespace LinkSet
+{
+	int fa[maxn];
+	void init() { for(int i=1;i<=n;i++) fa[i]=i; }
+	int ff(int x)
+	{
+		int a=x,b;
+		while(x!=fa[x]) x=fa[x];
+		while(a!=x)
+		{
+			b=fa[a];
+			fa[a]=x;
+			a=b;
+		}
+		return x;
+	}
+}
+namespace Kruskal
+{
+	struct EDGE { int u,v,w; };
+	inline bool operator<(const EDGE &a,const EDGE &b) { return a.w>b.w; }
+	vector<EDGE> e;
+	inline void AddEdge(int u,int v,int w) { e.push_back((EDGE){u,v,w}); }
+	void kruskal()
+	{
+		using namespace LinkSet;
+		sort(e.begin(),e.end());
+		int cnt=0,es=e.size();
+		for(int i=0;i<es&&cnt<n-1;i++)
+		{
+			int x=e[i].u,y=e[i].v,fx=ff(x),fy=ff(y);
+			if(fx==fy) continue;
+			fa[fx]=fy; cnt++;
+			::AddEdge(x,y,e[i].w); ::AddEdge(y,x,e[i].w);
+		}
+	}
+}
+bool vis[maxn];
+int f[maxn][21],w[maxn][21],deep[maxn];
+void dfs(int u,int fa)
+{
+	vis[u]=true;
+	for(Edge *it=G[u];it;it=it->next)
+	{
+		int v=it->v;
+		if(v==fa) continue;
+		f[v][0]=u;
+		w[v][0]=it->w;
+		deep[v]=deep[u]+1;
+		dfs(v,u);
+	}
+}
+int GetLCA(int x,int y)
+{
+	using namespace LinkSet;
+	if(ff(x)!=ff(y)) return -1;
+	int res=oo;
+	if(deep[x]<deep[y]) swap(x,y);
+	for(int i=20;i>=0;i--)
+		if(deep[f[x][i]]>=deep[y])
+		{
+			res=min(res,w[x][i]);
+			x=f[x][i];
+		}
+	if(x==y) return res;
+	for(int i=20;i>=0;i--)
+		if(f[x][i]!=f[y][i])
+		{
+			res=min(res,min(w[x][i],w[y][i]));
+			x=f[x][i];
+			y=f[y][i];
+		}
+	res=min(res,min(w[x][0],w[y][0]));
+	return res;
+}
+int main()
+{
+#ifdef local
+	freopen("pro.in","r",stdin);
+#endif
+	scanf("%d%d",&n,&m);
+	while(m-->0)
+	{
+		int x,y,z; scanf("%d%d%d",&x,&y,&z);
+		Kruskal::AddEdge(x,y,z);
+	}
+	LinkSet::init();
+	Kruskal::kruskal();
+	memset(w,0x3f,sizeof(w));
+	for(int i=1;i<=n;i++)
+		if(!vis[i])
+		{
+			deep[i]=1;
+			dfs(i,-1);
+		}
+	for(int i=1;i<=20;i++)
+		for(int j=1;j<=n;j++)
+		{
+			f[j][i]=f[f[j][i-1]][i-1];
+			w[j][i]=min(w[j][i-1],w[f[j][i-1]][i-1]);
+		}
+	scanf("%d",&q);
+	while(q-->0)
+	{
+		int x,y; scanf("%d%d",&x,&y);
+		printf("%d\n",GetLCA(x,y));
+	}
+	return 0;
+}