PAT1030. Travel Plan

Posted 2020-06-17

//晴神模板，dij+dfs，貌似最近几年PAT的的图论大体都这么干的，现在还在套用摸板阶段。。。。估计把这及格图论题题搞完，dij，dfs，并查集就掌握差不多了（模板还差不多）为何bfs能自己干出来，dfs就各种跪。。。。感觉需要把图论的经典算法都码一遍，才能有更深的理解，现在只是浅表

#include<cstdio>
#include<cstring>
#include<vector>
#include<algorithm>
using namespace std;
const int maxn=501;
const int INF=1<<30;
int n,m,st,ed,g[maxn][maxn],cost[maxn][maxn];
bool vis[maxn]={false};
int dist[maxn],mincost=INF;
vector<int >pre[maxn];
vector<int>path,tmppath;
void dij(int s)
{
int i,j;
fill(dist,dist+maxn,INF);
for(i=0;i<n;i++)pre[i].push_back(i);
dist[s]=0;
for(i=0;i<n;i++)
{
int min=INF,u=-1;
for(j=0;j<n;j++)
{
if(!vis[j]&&dist[j]<min)
{
min=dist[j];
u=j;
}
}
if(u==-1)return ;
vis[u]=true;
for(int v=0;v<n;v++)
{
if(!vis[v]&&g[u][v]!=INF)
{
if(dist[v]>dist[u]+g[u][v])
{
dist[v]=dist[u]+g[u][v];
pre[v].clear();
pre[v].push_back(u);
}
else if(dist[v]==dist[u]+g[u][v])pre[v].push_back(u);
}
}
}

}
void dfs(int v)
{
int i;
if(v==st)
{
tmppath.push_back(v);
int tmpcost=0;
for(i=tmppath.size()-1;i>0;i--)
{
int cur=tmppath[i],next=tmppath[i-1];
tmpcost+=cost[cur][next];
}
if(tmpcost<mincost)
{
mincost=tmpcost;
path=tmppath;
}
tmppath.pop_back();
return ;
}
tmppath.push_back(v);
for(i=0;i<pre[v].size();i++)dfs(pre[v][i]);
tmppath.pop_back();
}
int main()
{
freopen("input.txt","r",stdin);
while(scanf("%d%d%d%d",&n,&m,&st,&ed)!=EOF)
{
int i,a,b;
fill(g[0],g[0]+maxn*maxn,INF);
fill(cost[0],cost[0]+maxn*maxn,INF);
for(i=0;i<m;i++)
{
scanf("%d%d",&a,&b);
scanf("%d%d",&g[a][b],&cost[a][b]);
g[b][a]=g[a][b];
cost[b][a]=cost[a][b];
}
dij(st);
dfs(ed);
for(i=path.size()-1;i>=0;i--)
printf("%d ",path[i]);
printf("%d %d\n",dist[ed],mincost);
}
return 0;
}