洛谷P1396 营救 图论

洛谷P1396 营救

图论 dijkstra + 堆优化

#include <cstdio>
#include <cstring>
#include <cmath>
#include <cstdlib>
#include <string>
#include <algorithm>
#include <iomanip>
#include <iostream> 
#include <queue>
#include <vector>
using namespace std ; 

const int maxn = 10011 ,maxm = 20011,inf = 1e9 ; 
int n,m,s,t,cnt,x,y,v,ans ; 
struct node{
    int to,pre,val ; 
};
node e[2*maxm] ;  
int dist[maxn],vis[maxn],head[maxn] ; 

struct data{
    int dist,pos ;  
}; 

struct cmp{
    bool operator() (data a,data b) 
    {
        return a.dist > b.dist ; 
    }
};
priority_queue <data,vector<data>,cmp> Q ; 

inline void addedge(int x,int y,int v) 
{
    e[++cnt] = (node){ y,head[x],v } ;
    head[x] = cnt ; 
}

inline int dij(int s,int t) 
{
    int u,v ; 
    for(int i=1;i<=n;i++) dist[ i ] = inf ; 
    for(int i=1;i<=n;i++) vis[ i ] = false ; 
    data p ; 
    dist[ s ] = 0 ; 
    p = (data){ 0,s } ; 
    Q.push(p) ; 
    while(!Q.empty()) 
    {
        p = Q.top() ; 
        Q.pop() ;  
        //while(!Q.empty()&&vis[Q.top().pos]) Q.pop() ; 
        if(vis[p.pos]) continue ; 
        u = p.pos ; 
        vis[ u ] = 1 ; 
        for(int i=head[ u ];i;i = e[ i ].pre) 
        {
            v = e[ i ].to ; 
            dist[ v ] = min( max(e[ i ].val,dist[u]) , dist[ v ] ) ; 
            p = (data){ dist[v],v } ; 
            Q.push(p) ;  
        }
    }
    return dist[ t ] ; 
}

int main() 
{
    scanf("%d%d%d%d",&n,&m,&s,&t) ; 
    for(int i=1;i<=m;i++) 
    {
        scanf("%d%d%d",&x,&y,&v) ; 
        addedge(x,y,v) ; 
        addedge(y,x,v) ; 
    }
    
    ans = dij(s,t) ;  
    printf("%d
",ans) ; 
    return 0 ; 
}