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。。。。。

 1 // #pragma comment(linker, "/STACK:102c000000,102c000000")
 2 #include <iostream>
 3 #include <cstdio>
 4 #include <cstring>
 5 #include <sstream>
 6 #include <string>
 7 #include <algorithm>
 8 #include <list>
 9 #include <map>
10 #include <vector>
11 #include <queue>
12 #include <stack>
13 #include <cmath>
14 #include <cstdlib>
15 // #include <conio.h>
16 using namespace std;
17 #define pi acos(-1.0)
18 const int N = 1e5+10;
19 const int MOD = 1e9+7;
20 #define inf 0x7fffffff
21 typedef long long  LL;
22
23 void frein(){freopen("in.txt","r",stdin);}
24 void freout(){freopen("out.txt","w",stdout);}
25 inline int read(){int x=0,f=1;char ch=getchar();while(ch>‘9‘||ch<‘0‘) {if(ch==‘-‘) f=-1;ch=getchar();}while(ch>=‘0‘&&ch<=‘9‘) { x=x*10+ch-‘0‘;ch=getchar();}return x*f;}
26
27 int a[N];
28 int b[N];
29
30 int main(){
31     // frein();
32     // freout();
33     int n,m;
34     scanf("%d%d",&n,&m);
35     for(int i=1;i<=n;i++) scanf("%d",&a[i]);
36     for(int i=1;i<=m;i++) scanf("%d",&b[i]);
37     LL l=0,r=2e9;
38     while(l<r){
39        LL mid=(l+r)>>1;
40        int j=1;
41        bool flag=false;
42        for(int i=1;i<=n;i++){
43           if(j>m){
44             flag=true;
45             break;
46           }
47           if(fabs(b[j]-a[i])<=mid){
48             continue;
49           }
50           else{
51             j++;
52             i--;
53           }
54        }
55        if(flag){
56           l=mid+1;
57        }
58        else{
59           r=mid;
60        }
61     }
62     printf("%I64d\n",l);
63     return 0;
64 }