hdu 2962(最短路+二分）

#include<iostream>
#include<cstdio>
#include<queue>
#include<vector>
#include<algorithm>
const int MAXN=1000+10;
const int inf=1<<30;
using namespace std;
struct Node{
int v,w,h;
};
vector<Node>mp[MAXN];
int n,m;
int s,e;
int dist[MAXN];
bool visited[MAXN];

void SPFA(int u,int limit){
for(int i=1;i<=n;i++)dist[i]=inf;
dist[u]=0;
memset(visited,false,sizeof(visited));
queue<int>Q;
Q.push(u);
while(!Q.empty()){
int u=Q.front();
Q.pop();
visited[u]=false;
for(int i=0;i<mp[u].size();i++){
int v=mp[u][i].v;
int h=mp[u][i].h;
int w=mp[u][i].w;
if(h<limit)continue;//h应该尽量要大
if(dist[u]+w<dist[v]){
dist[v]=dist[u]+w;
if(!visited[v]){
Q.push(v);
visited[v]=true;
}
}
}
}
}

int main(){
int _case=1;
while(~scanf("%d%d",&n,&m)&&(n+m)){
if(_case>1)puts("");
for(int i=1;i<=n;i++)mp[i].clear();
for(int i=1;i<=m;i++){
int u,v,w,h;
scanf("%d%d%d%d",&u,&v,&h,&w);
Node p1,p2;
p1.v=u,p2.v=v;
p1.w=p2.w=w;
if(h==-1)h=inf;
p1.h=p2.h=h;
mp[u].push_back(p2);
mp[v].push_back(p1);
}
int limit;
scanf("%d%d%d",&s,&e,&limit);
//二分的时候得注意了，不知为什么wa了好多次
int low=0,high=limit,res=inf;
while(low<high){
int mid=(low+high+1)>>1;
SPFA(s,mid);
if(dist[e]==inf){
high=mid-1;
}else {
low=mid;
res=dist[e];
}
}
printf("Case %d:\n",_case++);
if(res==inf){
printf("cannot reach destination\n");
}else {
printf("maximum height = %d\n",low);
printf("length of shortest route = %d\n",res);
}
}
return 0;
}