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| #include <bits/stdc++.h> #define MAXN 500005 #define MOD 1000000007 #define int long long using namespace std; inline int read(){ int 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<<3)+(x<<1)+(ch^'0'); ch=getchar(); } return x*f; } int pow2[MAXN]; inline void Init(){ pow2[0]=1; for (register int i=1;i<MAXN;++i){ pow2[i]=(pow2[i-1]<<1)%MOD; } } namespace SegmentTree{ struct node{ int l,r; int v; }tree[MAXN*30]; #define lc(i) tree[i].l #define rc(i) tree[i].r inline void pushup(int i,int len){ tree[i].v=(tree[lc(i)].v+tree[rc(i)].v*pow2[len]%MOD)%MOD; } int tot; #define Lson lc(x),lc(y),L,mid #define Rson rc(x),rc(y),mid+1,R int Update(int x,int &y,int L,int R,int index){ y=++tot; lc(y)=lc(x),rc(y)=rc(x); if (L==R){ tree[y].v=tree[x].v^1; return tree[x].v; } int mid=(L+R)>>1,ans; if (index<=mid){ ans=Update(Lson,index); if (ans!=0) ans=Update(Rson,index); } else { ans=Update(Rson,index); } pushup(y,mid-L+1); return ans; } bool Compare(int x,int y,int L,int R){ if (L==R) { return tree[x].v>tree[y].v; } int mid=(L+R)>>1; if (tree[rc(x)].v==tree[rc(y)].v){ return Compare(Lson); } else { return Compare(Rson); } } } using namespace SegmentTree; int maxn; struct Node{ int u,rt; }; bool operator < (Node A,Node B){ return Compare(A.rt,B.rt,0,maxn); } struct Edge{ int to,len; }; vector<Edge>G[MAXN]; inline void AddEdge(int u,int v,int w){ Edge temp; temp.to=v,temp.len=w; G[u].push_back(temp); } int vis[MAXN],dis[MAXN],rt[MAXN],pre[MAXN],dep[MAXN]; int s,t; void Out(int u,int dep){ if (u==s){printf("%I64d\n%I64d ",dep,s);return ;} Out(pre[u],dep+1); printf("%I64d ",u); } #undef int int main(){ #define int long long Init(); int n=read(),m=read(); for (register int i=1;i<=m;++i){ int u=read(),v=read(),w=read(); AddEdge(u,v,w); AddEdge(v,u,w); maxn=max(maxn,w); } maxn+=log2(m)+1; s=read(),t=read(); priority_queue<Node>Q; Q.push(Node{s,0}); while (Q.size()){ int u=Q.top().u,R=Q.top().rt; Q.pop(); if (vis[u]) continue; vis[u]=true; for (register int i=0;i<G[u].size();++i){ int v=G[u][i].to,w=G[u][i].len,_rt=0; Update(R,_rt,0,maxn,w); if (!rt[v]||Compare(rt[v],_rt,0,maxn)){ rt[v]=_rt,pre[v]=u; dep[v]=dep[u]+1; Q.push(Node{v,rt[v]}); } } } if (!vis[t]){ printf("-1\n"); } else { printf("%I64d\n",tree[rt[t]].v); Out(t,1); } }
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