hdu 2962

二分加最短路

#include <stdio.h>
#include <string.h>
#define N 1005
#define INF 0x3f3f3f3f
struct tt{
    int h,cost;
}dis[N][N];
int vis[N],d[N],num =1;
int dijkstral(int v0,int t,int n,int h)
{
    int i,temp,x,y;
    for(i = 1 ; i <= n ; i++)
    {
        if(dis[v0][i].h>=h){
            d[i] = dis[v0][i].cost;
        }else d[i] = INF;
        vis[i] = 0;
    }
    d[v0] = 0;
    vis[v0] = 1;
    for(i = 1 ; i <= n ; i++)
    {
        temp = INF ;
        for(y = 1 ; y <= n ; y++)
           if(!vis[y] && temp>d[y]) temp = d[x=y];
        if(temp == INF) return 0;
            vis[x] = 1;
            if(x == t) return 1;
        for(y = 1 ; y <= n ; y++)
            if(!vis[y] &&dis[x][y].cost+d[x]<d[y]&&dis[x][y].h>=h)
                d[y] = d[x] + dis[x][y].cost;
    }
    return 0;
}
int main()
{
    int R,C,s,t,h_limit,i,j,cas = 1;
    while(~scanf("%d %d",&C,&R),C+R)
    {
        for(i = 1 ; i <= C ; i++)
        {
            for(j = 1 ; j <= C ; j++)
            {
                dis[i][j].cost = (i == j) ?0:INF;
                dis[i][j].h = 0;
            }
        }
        while(R--)
        {
            int x,y,h,val;
            scanf("%d %d %d %d",&x,&y,&h,&val);
            if(h == -1) h = INF;
            dis[x][y].cost = dis[y][x].cost = val;
            dis[x][y].h = dis[y][x].h = h;
        }
        scanf("%d %d %d",&s,&t,&h_limit);
        int l = 1 ,r = h_limit,mid,ans;
        while(l<=r)
        {
            mid = l+(r-l)/2;
            if(dijkstral(s,t,C,mid)){
                ans = d[t];
                l = mid+1;
            }else r = mid-1;
        }
        if(cas>1) printf("
");
        printf("Case %d:
",cas++);
        if(r<=0) printf("cannot reach destination
");
        else {
            printf("maximum height = %d
",r);
            printf("length of shortest route = %d
",ans);
        }

    }
    return 0;
}