103 lines
2.1 KiB
C++
103 lines
2.1 KiB
C++
#include<cstdio>
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#include<cstring>
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#include<queue>
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#include<set>
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#include<algorithm>
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using namespace std;
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const int MAXN = 5e5+5;
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const int INF = 0x3f3f3f3f;
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typedef long long LL;
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int head[MAXN],e;
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LL dis[MAXN];
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bool vis[MAXN];
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struct Edge{
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int v,nxt,w;
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}E[MAXN<<1];
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void init()
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{
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e=0;
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memset(head,-1,sizeof head);
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memset(vis,false,sizeof vis);
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}
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void add(int u,int v,int w)
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{
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E[e].v = v;
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E[e].w = w;
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E[e].nxt = head[u];
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head[u] = e++;
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}
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struct QNode{
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int v,c;
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QNode(int _v,int _c){
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v = _v;c=_c;
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}
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bool operator < (const QNode &a) const{
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return c>a.c;
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}
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};
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LL dijkstra(int n)
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{
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memset(dis,INF,sizeof dis);
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priority_queue<QNode>Q;
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dis[1] = 0;
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Q.push(QNode(1,0));
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while(!Q.empty())
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{
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QNode tmp = Q.top();Q.pop();
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int u = tmp.v;
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if(vis[u]) continue;
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vis[u] = true;
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for(int i=head[u];~i;i=E[i].nxt){
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int v = E[i].v;
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int w = E[i].w;
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if(vis[v]) continue;
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if(dis[u]+w<dis[v]){
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dis[v] = dis[u]+w;
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Q.push(QNode(v,dis[v]));
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}
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}
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}
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return dis[n];
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}
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LL BFS(int n,LL val)
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{
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set<int>ta,tb;
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queue<int>Q;Q.push(1);
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dis[1] = 0,dis[n] = INF;
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for(int i=2;i<=n;i++) ta.insert(i);
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while(!Q.empty())
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{
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int u = Q.front();Q.pop();
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for(int i=head[u];~i;i=E[i].nxt){
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int v = E[i].v;
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if(!ta.count(v)) continue;
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ta.erase(v);tb.insert(v);
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}
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for(set<int>::iterator it=ta.begin();it!=ta.end();it++){
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Q.push(*it);
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dis[*it] = dis[u] + val;
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}
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ta.swap(tb);tb.clear();
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}
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return dis[n];
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}
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int main()
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{
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int N,M;
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LL A,B;
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int u,v;
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while(~scanf("%d%d%lld%lld",&N,&M,&A,&B))
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{
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init();
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bool flag = false;
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for(int i=0;i<M;i++){
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scanf("%d%d",&u,&v);
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add(u,v,A);add(v,u,A);
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if(min(u,v)==1&&max(u,v)==N)flag =true;
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}
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if(!flag) printf("%lld\n",min(dijkstra(N),(LL)B));
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else printf("%lld\n",min(BFS(N,B),(LL)A));
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}
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return 0;
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}
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