1379. Cups Transportation

http://acm.timus.ru/problem.aspx?space=1&num=1379

二分 最短路

代码：

#include<iostream>
#include<cstdio>
#include<cstring>
#include<string>
#include<map>
#include<vector>
#include<stack>
#include<set>
#include<map>
#include<queue>
#include<algorithm>
#include<cmath>
#define LL long long
#define sint short int
//#pragma comment(linker, "/STACK:1024000000,1024000000")
using namespace std;
const int N=505;
const int T=1440;
const int INF=1000000000;
int head[N],I;
bool had[N];
int dist[N];
int cost[N][N];
int limi[N][N];
int dijkstra(int x1,int x2,int n,int limit)
{
    for(int i=1;i<=n;++i)
    dist[i]=INF;
    memset(had,false,sizeof(had));
    dist[x1]=0;
    for(int w=1;w<=n;++w)
    {
        int k=-1;
        for(int i=1;i<=n;++i)
        if(!had[i]&&(k==-1||dist[i]<dist[k]))
        k=i;
        if(k==x2||dist[k]==INF)
        break;
        had[k]=true;
        for(int i=1;i<=n;++i)
        if(!had[i]&&limi[k][i]>=limit&&dist[k]+cost[k][i]<dist[i])
        dist[i]=dist[k]+cost[k][i];
    }
    return dist[x2];
}
int main()
{
    //freopen("data.in","r",stdin);
    int n,m;
    cin>>n>>m;
    for(int i=1;i<=n;++i)
    for(int j=1;j<=n;++j)
    {limi[i][j]=0;cost[i][j]=INF;}
    int l=1,r=0;
    while(m--)
    {
        int i,j,t,g;
        cin>>i>>j>>t>>g;
        g=max((g-3000000)/100,0);
        cost[i][j]=cost[j][i]=t;
        limi[i][j]=limi[j][i]=g;
        r=max(r,g);
    }
    if(n==1)
    {cout<<"10000000"<<endl;return 0;}
    while(l<=r)
    {
        int mid=(l+r)/2;
        if(dijkstra(1,n,n,mid)<=T)
        l=mid+1;
        else
        r=mid-1;
    }
    cout<<r<<endl;
    return 0;
}