hdu4004（二分）

#include <cstdio>
#include <cstring>
#include <cmath>
#include <algorithm>
#include <queue>
#include <cstdlib>
#include <vector>
#include <set>
#include <map>
#define LL long long
#define inf 1<<30
using namespace std;

int n,m,l,a[500010];
int judge(int x)
{
    int res=0,temp=0;
    for(int i=1;i<=n;i++)
    {
        if(a[i]-temp>x)return 0;
        while(a[i]-temp<=x&&i<=n)i++;
        temp=a[i-1];i--;
        res++;
    }
    return res<=m;
}
int main()
{
    while(scanf("%d%d%d",&l,&n,&m)>0)
    {
        for(int i=1;i<=n;i++)scanf("%d",&a[i]);
        a[++n]=l;
        sort(a+1,a+n+1);
        int left=0,right=l,mid,ans;
        while(left<=right)
        {
            mid=(left+right)/2;
            if(judge(mid))
                right=mid-1,ans=mid;
            else left=mid+1;
        }
        printf("%d\n",ans);
    }
}