codeforce 702C Cellular Network 二分答案

http://codeforces.com/contest/702

题意：n个村庄，m个机站，问机站最短半径覆盖完所有村庄

思路：直接二分答案

二分太弱，调了半天。。。。。

 // #pragma comment(linker, "/STACK:102c000000,102c000000")
 #include <iostream>
 #include <cstdio>
 #include <cstring>
 #include <sstream>
 #include <string>
 #include <algorithm>
 #include <list>
 #include <map>
 #include <vector>
 #include <queue>
 #include <stack>
 #include <cmath>
 #include <cstdlib>
 // #include <conio.h>
 using namespace std;
 #define pi acos(-1.0)
 const int N = 1e5+;
 const int MOD = 1e9+;
 #define inf 0x7fffffff
 typedef long long  LL;

 void frein(){freopen("in.txt","r",stdin);}
 void freout(){freopen("out.txt","w",stdout);}
 inline int read(){int x=,f=;char ch=getchar();while(ch>''||ch<'') {if(ch=='-') f=-;ch=getchar();}while(ch>=''&&ch<='') { x=x*+ch-'';ch=getchar();}return x*f;}

 int a[N];
 int b[N];

 int main(){
     // frein();
     // freout();
     int n,m;
     scanf("%d%d",&n,&m);
     for(int i=;i<=n;i++) scanf("%d",&a[i]);
     for(int i=;i<=m;i++) scanf("%d",&b[i]);
     LL l=,r=2e9;
     while(l<r){
        LL mid=(l+r)>>;
        int j=;
        bool flag=false;
        for(int i=;i<=n;i++){
           if(j>m){
             flag=true;
             break;
           }
           if(fabs(b[j]-a[i])<=mid){
             continue;
           }
           else{
             j++;
             i--;
           }
        }
        if(flag){
           l=mid+;
        }
        else{
           r=mid;
        }
     }
     printf("%I64d\n",l);
     return ;
 }