【PAT】1003. Emergency

考查点：Dijkstra算法

思路：直接用Dijkstra算法，但是·要增加num数组记录每个点到起点的最短路径数，判断时候在相等时也要更新，同样还要增加权值点的数组和最短路径的总权值数组来更新最大权值，注意对起点各个参数的初始化。增加如下代码即可：

if(vis[v]==false&&d[u]+G[u][v]<d[v]){                d[v]=d[u]+G[u][v];                ww[v]=ww[u]+w[v];                num[v]=num[u];            }else if(d[u]+G[u][v]==d[v]){                if(ww[u]+w[v]>ww[v])                    ww[v]=ww[u]+w[v];                num[v]+=num[u];            }存储结构应用邻接矩阵：
#define LOCAL#include <iostream>#include <cstdio>#include <cstring>#include <algorithm>#include <cmath>#include <string>#include <vector>#include <map>#include <set>#include <queue>#include <stack>#define FOR(i, x, y) for(int i = x; i <= y; i++)#define rFOR(i, x, y) for(int i = x; i >= y; i--)#define MAXN 600#define oo 0x3f3f3f3fusing namespace std;int n,m;int num[MAXN];int G[MAXN][MAXN];int d[MAXN];int w[MAXN];int ww[MAXN];int vis[MAXN];void Dijkstra(int s){    fill(d,d+MAXN,oo);    d[s]=0;    ww[s]=w[s];    num[s]=1;    for(int i=0;i<n;i++){        int u=-1,MIN=oo;        for(int j=0;j<n;j++){            if(vis[j]==false&&d[j]<MIN){                u=j;MIN=d[j];            }        }        if(u==-1)return;        vis[u]=true;        for(int v=0;v<n;v++){            if(vis[v]==false&&d[u]+G[u][v]<d[v]){                d[v]=d[u]+G[u][v];                ww[v]=ww[u]+w[v];                num[v]=num[u];            }else if(d[u]+G[u][v]==d[v]){                if(ww[u]+w[v]>ww[v])                    ww[v]=ww[u]+w[v];                num[v]+=num[u];            }        }    }}int main(){    #ifdef LOCAL        freopen("data.in","r",stdin);        freopen("data.out","w",stdout);    #endif // LOCAL    int c1,c2;    scanf("%d%d%d%d",&n,&m,&c1,&c2);    fill(G[0],G[0]+MAXN*MAXN,oo);    FOR(i,0,n-1)    {        scanf("%d",&w[i]);    }    FOR(i,1,m)    {        int u,v,w;        scanf("%d%d%d",&u,&v,&w);        G[u][v]=w,G[v][u]=w;    }    Dijkstra(c1);    PRintf("%d %d",num[c2],ww[c2]);    return 0;}