2016夏季练习——二分

来源：POJ2456

二分水题

#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>

using namespace std;

const int MAXN = 100000+10;
int n,m;
int a[MAXN];
bool judge(int d){
	int cnt=1;
	int len=a[0]+d;
	for(int i=0;i<n;i++){
		if(a[i]>=len){
			len=a[i]+d;
			cnt++;
		}
	}
	if(cnt>=m) return 1;
	return 0;
}
int main(){
	while(scanf("%d%d",&n,&m)!=EOF){
		for(int i=0;i<n;i++){
			scanf("%d",a+i);
		}
		sort(a,a+n);
		int left=0;
		int right=a[n-1]-a[0];
		int mid;
		int ans;
		while(left<=right) {
		    mid=(left+right)/2;
		    if(judge(mid)){
		    	left=mid+1;
		    	ans=mid;
		    }
		    else{
		    	right=mid-1;
		    }
		   // cout<<left<<" "<<mid<<" "<<right<<endl;
		}
		cout<<ans<<endl;
	}
	return 0;
}