HDU1595 - find the longest of the shortest - dijkstra+记录路径

AC代码

#include<iostream>
#include<stdio.h>
#include<string.h>
using namespace std;
#define inf 0x3f3f3f3f

int book[1010],dist[1010],e[1010][1010],pre[1010];
int n,m;
bool flag;

void dijkstra()
{
    for(int i=1; i<=n; i++)
    {
        //dist[i]=e[1][i];
        dist[i]=inf;
        book[i]=0;
    }
    //book[1]=1;
    dist[1]=0;
    int u;
    for(int i=2; i<=n; i++)
    {
        int minn=inf;
        for(int j=1; j<=n; j++)
        {
            if(book[j]==0&&minn>dist[j])
            {
                u=j;
                minn=dist[j];
            }
        }
        if(minn==inf)
            break;
        book[u]=1;
        for(int j=1; j<=n; j++)
        {
            if(book[j]==0&&e[u][j]<inf)
            {
                if(dist[u]+e[u][j]<dist[j])
                {
                    dist[j]=dist[u]+e[u][j];
                    if(flag==0)
                        pre[j]=u;
                }
            }
        }
    }
}

int main()
{
    while(cin>>n>>m)
    {
        for(int i=1; i<=n; i++)
        {
            pre[i]=-1;
            for(int j=1; j<=n; j++)
            {
               
                if(i==j)
                    e[i][j]=0;
                else
                    e[i][j]=inf;
            }
        }
        for(int i=1; i<=m; i++)
        {
            int a,b,c;
            cin>>a>>b>>c;
            e[a][b]=e[b][a]=min(e[a][b],c);
        }
        flag=0,dijkstra();
        flag=1;
        int x=dist[n];
      //  pre[1]=1;
        for(int i=n; i!=-1; i=pre[i])
        {
            int t=e[i][pre[i]];
            e[i][pre[i]]=e[pre[i]][i]=inf;
            dijkstra();
            if(dist[n]!=inf)
                x=max(x,dist[n]);
            e[i][pre[i]]=e[pre[i]][i]=t;
        }
        cout<<x<<endl;
    }
    return 0;
}