HDU 2066 一个人的旅行

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http://acm.hdu.edu.cn/showproblem.php?pid=2066

迪杰斯特拉算法实现（400MS）：

#include <stdio.h>#include <string.h>#include <iostream>#include <algorithm>using namespace std;const int MAX = 1001;int V,E,G[1010][1010],dis[1010],vis[1010];int u[1010],v[1010];void dijkstra(int scr){    for(int i=0; i<MAX; i++){        dis[i] = G[scr][i];        vis[i] = 0;    }    vis[scr] = 1;    for(int i=0; i<V-1; i++){        int tmp = 1e9, k = scr;        for(int j=1; j<=V; j++){            if(vis[j])  continue;            if(dis[j] < tmp){                tmp = dis[j];                k = j;            }        }//        cout << tmp << endl;        vis[k] = 1;        for(int j=1; j<=V; j++){            if(vis[j])  continue;            dis[j] = min(dis[j], dis[k] + G[k][j]);        }    }}int main(){//    freopen("in.txt", "r", stdin);    int a,b;    while(scanf("%d%d%d",&E,&a,&b) == 3){        for(int i=1; i<MAX; i++){            for(int j=1; j<MAX; j++){                G[i][j] = 1e9;            }            G[i][i] = 0;        }        for(int i=0; i<E; i++){            int from,to,cost;            scanf("%d%d%d",&from,&to,&cost);            V = max(V, max(from, to));            G[from][to] = G[to][from] = min(G[from][to],cost);        }        for(int i=0; i<a; i++){            scanf("%d",&u[i]);        }        for(int i=0; i<b; i++){            scanf("%d",&v[i]);        }        int ans = 1e9;        for(int i=0; i<a; i++){            dijkstra(u[i]);            for(int j=0; j<b; j++)                ans = min(ans, dis[v[j]]);        }        printf("%d\n",ans);    }    return 0;}

SPFA实现（0MS）：

#include <queue>#include <stdio.h>#include <string.h>#include <iostream>#include <algorithm>using namespace std;struct edge{    int to;    int cost;    int next;}adj[2000010];int num,head[1010],a,b,c,V;void addedge(int from, int to, int cost){    adj[num].to = to;    adj[num].cost = cost;    adj[num].next = head[from];    head[from] = num++;}int dis[1010],vis[1010],enter[1010];bool SPFA(int scr){    for(int i=1; i<=V; i++){        dis[i] = 1e9;        vis[i] = 0;        enter[i] = 0;    }    dis[scr] = 0;    vis[scr] = 1;    enter[scr] = 1;    queue <int> Q;    Q.push(scr);    while(!Q.empty()){        int tmp = Q.front();        Q.pop();        vis[tmp] = 0;        for(int i=head[tmp]; i!=-1; i=adj[i].next){            if(dis[adj[i].to] > dis[tmp] + adj[i].cost){                dis[adj[i].to] = dis[tmp] + adj[i].cost;                if(!vis[dis[adj[i].to]]){                    vis[adj[i].to] = 1;                    enter[adj[i].to]++;                    if(enter[adj[i].to] >= V)                        return false;                    Q.push(adj[i].to);                }            }        }    }    return true;}int u[1010],v[1010];int main(){//    freopen("in.txt", "r", stdin);    while(scanf("%d%d%d",&a,&b,&c) == 3){        memset(head, -1, sizeof(head));        num = 0;        for(int i=0; i<a; i++){            int from, to, cost;            scanf("%d%d%d",&from,&to,&cost);            V = max(V, max(from, to));            addedge(from, to, cost);            addedge(to, from, cost);        }        for(int i=0; i<b; i++)            scanf("%d",&u[i]);        for(int i=0; i<c; i++)            scanf("%d",&v[i]);        int ans = 1e9;        for(int i=0; i<b; i++){            SPFA(u[i]);            for(int j=0; j<c; j++)                ans = min(ans, dis[v[j]]);        }        printf("%d\n",ans);    }    return 0;}

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