[BZOJ2763][JLOI2011]飞行路线（图论）

题目：

我是超链接

题解：

分层图来一波！就是在裸dij的基础上加了一步，可以往下一层转移状态

代码：

#include <queue>#include <cstdio>#include <cstring>#include <iostream>using namespace std;const int N=50005;struct hh{int x,c,dis;};int tot,nxt[N*2],point[N],v[N*2],c[N*2];int s,t,dis[10005][15],k;bool vis[10005][15];bool operator <(const hh a,const hh b){return a.dis>b.dis;}void addline(int x,int y,int z){    ++tot; nxt[tot]=point[x]; point[x]=tot; v[tot]=y; c[tot]=z;    ++tot; nxt[tot]=point[y]; point[y]=tot; v[tot]=x; c[tot]=z;}int dij(){    priority_queue<hh>q;    memset(dis,0x7f,sizeof(dis));    memset(vis,0,sizeof(vis));    dis[s][0]=0;    q.push((hh){s,0,0});    while (!q.empty())    {        hh now=q.top(); q.pop();        if (vis[t][k]) return dis[t][k];        if (vis[now.x][now.c]) continue;        vis[now.x][now.c]=1;            for (int i=point[now.x];i;i=nxt[i])        {            if (dis[v[i]][now.c]>dis[now.x][now.c]+c[i])            {                dis[v[i]][now.c]=dis[now.x][now.c]+c[i];                q.push((hh){v[i],now.c,dis[v[i]][now.c]});            }            if (now.c+1<=k) dis[v[i]][now.c+1]=now.dis,q.push((hh){v[i],now.c+1,now.dis});        }             }}int main(){    int n,m,i;    scanf("%d%d%d",&n,&m,&k);    scanf("%d%d",&s,&t);s++; t++;    for (i=1;i<=m;i++)    {        int x,y,z;        scanf("%d%d%d",&x,&y,&z);        addline(x+1,y+1,z);    }    printf("%d",dij());}