hdu 2544 hdu 1874 poj 2387 Dijkstra 模板题

hdu 2544 

求点1到点n的最短路  无向图

Sample Input
2 1 //结点数 边数
1 2 3 //u v w
3 3
1 2 5
2 3 5
3 1 2
0 0

Sample Output
3
2

 

堆优化Dijstra模板

# include <iostream>
# include <cstdio>
# include <cstring>
# include <algorithm>
# include <cmath>
# include <queue>
# define LL long long
using namespace std ;

const int INF=0x3f3f3f3f;
const int MAXN=110;
struct qnode
{
    int v;
    int c;
    qnode(int _v=0,int _c=0):v(_v),c(_c){}
    bool operator <(const qnode &r)const
    {
        return c>r.c;
    }
};
struct Edge
{
    int v,cost;
    Edge(int _v=0,int _cost=0):v(_v),cost(_cost){}
};
vector<Edge>E[MAXN];
bool vis[MAXN];
int dist[MAXN];
int n ;
void Dijkstra(int start)//点的编号从1开始
{
    memset(vis,false,sizeof(vis));
    for(int i=1;i<=n;i++)dist[i]=INF;
    priority_queue<qnode>que;
    while(!que.empty())que.pop();
    dist[start]=0;
    que.push(qnode(start,0));
    qnode tmp;
    while(!que.empty())
    {
        tmp=que.top();
        que.pop();
        int u=tmp.v;
        if(vis[u])continue;
        vis[u]=true;
        for(int i=0;i<E[u].size();i++)
        {
            int v=E[tmp.v][i].v;
            int cost=E[u][i].cost;
            if(!vis[v]&&dist[v]>dist[u]+cost)
            {
                dist[v]=dist[u]+cost;
                que.push(qnode(v,dist[v]));
            }
        }
    }
}
void addedge(int u,int v,int w)
{
    E[u].push_back(Edge(v,w));
}

int main ()
{
   // freopen("in.txt","r",stdin) ;
    int m ;
    while (scanf("%d %d" , &n , &m) !=EOF)
    {
        if (n==0 && m==0)
            break ;
        int u , v , w ;
        int i , j ;
        for(i=1;i<=n;i++)
            E[i].clear();

         while(m--)
        {
            scanf("%d%d%d" , &u , &v , &w) ;
            addedge(u,v,w) ;
            addedge(v,u,w) ;
        }
        Dijkstra(1) ;
        printf("%d\n" , dist[n]) ;
    }

    return 0 ;
}

 

hdu 1874

输出最短需要行走的距离。如果不存在从S到T的路线，就输出-1.

这题有重边

Sample Input
3 3 //结点数 边数
0 1 1//u v w
0 2 3
1 2 1
0 2 //起点 终点
3 1
0 1 1
1 2

Sample Output
2
-1

 

# include <iostream>
# include <cstdio>
# include <cstring>
# include <algorithm>
# include <cmath>
# define LL long long
using namespace std ;

const int MAXN=300;
const int INF=0x3f3f3f3f;
int n ;
bool vis[MAXN];
int cost[MAXN][MAXN] ;
int lowcost[MAXN] ;
int pre[MAXN];
void Dijkstra(int beg)
{
    for(int i=0;i<n;i++)
    {
        lowcost[i]=INF;vis[i]=false;pre[i]=-1;
    }
    lowcost[beg]=0;
    for(int j=0;j<n;j++)
    {
        int k=-1;
        int Min=INF;
        for(int i=0;i<n;i++)
            if(!vis[i]&&lowcost[i]<Min)
            {
                Min=lowcost[i];
                k=i;
            }
            if(k==-1)
                break ;
            vis[k]=true;
            for(int i=0;i<n;i++)
                if(!vis[i]&&lowcost[k]+cost[k][i]<lowcost[i])
                {
                    lowcost[i]=lowcost[k]+cost[k][i];
                        pre[i]=k;
                }
    }

}

int main ()
{
  //  freopen("in.txt","r",stdin) ;
    int m ;
    while (scanf("%d %d" , &n , &m) !=EOF)
    {

        int u , v , w ;
        int i , j ;
        for (i = 0 ; i < n ; i++)
            for (j = 0 ; j < n ; j++)
               cost[i][j] = INF ;
        while(m--)
        {
            scanf("%d%d%d" , &u , &v , &w) ;
            if (w < cost[u][v]) //防止重边
            {
                cost[u][v] = w ;
                cost[v][u] = w ;
            }
        }
        scanf("%d %d" , &u , &v) ;
        Dijkstra(u) ;
        if (lowcost[v] != INF)
           printf("%d\n" , lowcost[v]) ;
        else
           printf("-1\n") ;
    }

    return 0 ;
}

 

poj 2387

有重边  无向图 

Sample Input

5 5 // m n
1 2 20 //u v w
2 3 30
3 4 20
4 5 20
1 5 100
Sample Output

90

 

# include <iostream>
# include <cstdio>
# include <cstring>
# include <algorithm>
# include <cmath>
# define LL long long
using namespace std ;

const int MAXN=1100;
const int INF=0x3f3f3f3f;
int n ;
bool vis[MAXN];
int cost[MAXN][MAXN] ;
int lowcost[MAXN] ;
int pre[MAXN];
void Dijkstra(int beg)
{
    for(int i=0;i<n;i++)
    {
        lowcost[i]=INF;vis[i]=false;pre[i]=-1;
    }
    lowcost[beg]=0;
    for(int j=0;j<n;j++)
    {
        int k=-1;
        int Min=INF;
        for(int i=0;i<n;i++)
            if(!vis[i]&&lowcost[i]<Min)
            {
                Min=lowcost[i];
                k=i;
            }
            if(k==-1)
                break ;
            vis[k]=true;
            for(int i=0;i<n;i++)
                if(!vis[i]&&lowcost[k]+cost[k][i]<lowcost[i])
                {
                    lowcost[i]=lowcost[k]+cost[k][i];
                        pre[i]=k;
                }
    }

}

int main ()
{
   // freopen("in.txt","r",stdin) ;
    int m ;
    while (scanf("%d %d" , &m , &n) !=EOF)
    {

        int u , v , w ;
        int i , j ;
        for (i = 0 ; i < n ; i++)
        for (j = 0 ; j < n ; j++)
       {
           if (i == j)
              cost[i][j] = 0 ;
           else
              cost[i][j] = INF ;
       }
        while(m--)
        {
            scanf("%d%d%d" , &u , &v , &w) ;
            if (w < cost[u-1][v-1]) //防止重边
            {
                cost[u-1][v-1] = w ;
                cost[v-1][u-1] = w ;
            }
        }
        Dijkstra(n-1) ;
        if (lowcost[0] != INF)
           printf("%d\n" , lowcost[0]) ;

    }

    return 0 ;
}