bzoj千题计划226：bzoj2763: [JLOI2011]飞行路线

#include<queue>
#include<cstdio>
#include<cstring>
#include<iostream>
#include<algorithm>

using namespace std;

#define N 10001
#define M 50001

int n,k;
int S,T;

int tot;
int front[N],nxt[M<<1],to[M<<1],val[M<<1];

int dp[N][11];
bool vis[N][11];

struct node
{
    int pos,rest;
    int dis;

    node(int Pos=0,int Rest=0,int Dis=0):pos(Pos),rest(Rest),dis(Dis){}
        
    bool operator < (node p) const
    {
        return dis>p.dis;
    }
}now;
priority_queue<node>q;

void read(int &x)
{
    x=0; char c=getchar();
    while(!isdigit(c)) c=getchar();
    while(isdigit(c)) { x=x*10+c-‘0‘; c=getchar(); }
}

void add(int u,int v,int w)
{
    to[++tot]=v; nxt[tot]=front[u]; front[u]=tot; val[tot]=w;
    to[++tot]=u; nxt[tot]=front[v]; front[v]=tot; val[tot]=w;
}

void dijkstra()
{
    memset(dp,63,sizeof(dp));
    dp[S][k]=0;
    now.pos=S;
    now.rest=k;
    q.push(now);
    int u,v,cnt;
    while(!q.empty())
    {
        now=q.top();
        q.pop();
        u=now.pos;
        cnt=now.rest;
        if(vis[u][cnt]) continue;
        vis[u][cnt]=true;
        for(int i=front[u];i;i=nxt[i])
        {
            v=to[i];
            if(dp[u][cnt]+val[i]<dp[v][cnt])
            {
                dp[v][cnt]=dp[u][cnt]+val[i];
                q.push(node(v,cnt,dp[v][cnt]));
            }
            if(cnt && dp[u][cnt]<dp[v][cnt-1])
            {
                dp[v][cnt-1]=dp[u][cnt];
                q.push(node(v,cnt-1,dp[v][cnt-1]));
            }
        }
    }
}

int main()
{
    int m;
    read(n); read(m); read(k);
    read(S); read(T);
    int u,v,w;
    while(m--)
    {
        read(u); read(v); read(w);
        add(u,v,w);
    }
    dijkstra();
    int ans=1e9;
    for(int i=0;i<=k;++i) ans=min(ans,dp[T][i]);
    printf("%d",ans);
}