HDU 2962

Dijstra 

1.设定mid=left+(right-left+1)等，二分可以根据自己的需求，产生很好的灵活性

2.其实题目也没有说清楚，这个第二个输出实在模棱两可

#include<iostream>
#include<cstring>
#include<cstdio>
#include<vector>
#include<algorithm>
#include<queue>
#include<map>
#define INF 1e9
using namespace std;
const int maxn = 1000+10;
const int maxm = 1000000+10;
struct Edge
{
    int from,to,height,dist;
    Edge(int f,int t,int h,int d):from(f),to(t),height(h),dist(d){}
};

struct HeapNode
{
    int d,u;
    HeapNode(int d,int u):d(d),u(u){}
    bool operator<(const HeapNode&rhs)const
    {
        return d>rhs.d;
    }
};

struct Dijkstra
{
    int n,m;
    vector<Edge> edges;
    vector<int> G[maxn];
    bool done[maxn];
    int d[maxn];

    void init(int n)
    {
        this->n=n;
        for(int i=1;i<=n;i++) G[i].clear();
        edges.clear();
    }

    void AddEdge(int from,int to,int height,int dist)
    {
        edges.push_back(Edge(from,to,height,dist));
        m = edges.size();
        G[from].push_back(m-1);
    }

    int dijkstra(int s,int e,int limit)
    {
        if(s==e) return 0;
        priority_queue<HeapNode> Q;
        for(int i=1;i<=n;i++) d[i]=INF;
        d[s]=0;
        memset(done,0,sizeof(done));
        Q.push(HeapNode(d[s],s));

        while(!Q.empty())
        {
            HeapNode x=Q.top(); Q.pop();
            int u=x.u;
            if(done[u]) continue;
            done[u]=true;

            for(int i=0;i<G[u].size();i++)
            {
                Edge &e=edges[G[u][i]];
                int cur_lmt=e.height;
                if(d[e.to] > d[u]+e.dist&&(cur_lmt>=limit||cur_lmt==-1))
                {
                    d[e.to] = d[u]+e.dist;
                    Q.push(HeapNode(d[e.to],e.to));
                }
            }
        }
        if(d[e]==INF) return -1;
        return d[e];
    }
}DJ;
int n,m;

int main()
{
    int cas=1;
    while(scanf("%d%d",&n,&m))
    {
        if(!n&&!m)break;
        DJ.init(n);
        for(int i=0;i<m;i++)
        {
            int u,v,h,c;
            scanf("%d%d%d%d",&u,&v,&h,&c);
            DJ.AddEdge(u,v,h,c);
            DJ.AddEdge(v,u,h,c);
        }
        int u,v,h;
        scanf("%d%d%d",&u,&v,&h);
        int left=0,right=h;
        while(left!=right)
        {
            int mid=left+(right-left+1)/2;
            if(DJ.dijkstra(u,v,mid)==-1)right=mid-1;
            else left=mid;
        }
        int ans=left;
        if(cas>=2)printf("\n");
        printf("Case %d:\n",cas++);
        if(ans>0)
            printf("maximum height = %d\nlength of shortest route = %d\n",ans,DJ.dijkstra(u,v,ans));
        else
            printf("cannot reach destination\n\n");
    }
    return 0;
}