poj 3258River Hopscotch

#include<iostream>
#include<cstdio>
#include<cmath>
#include<cstring>
#include<algorithm>
using namespace std;
const int maxn=1e5+5;
int c[maxn];
int lo,n,m;

bool judge(int x){
    int t=0,last=0;
    for(int i=0;i<n;i++)
      if(c[i]-last>=x){
          t++;
          last=c[i];
          if(t==n-m)
            break;
      }
    return (t==(n-m))&&(lo-last>=x);
}

int main(){
    while(~scanf("%d%d%d",&lo,&n,&m)){
        for(int i=0;i<n;i++)
          scanf("%d",c+i);
        sort(c,c+n);
        int l=0,r=lo;
        while(r-l>0){
            int mid=l+(r-l+1)/2;
            if(judge(mid))
              l=mid;
            else
              r=mid-1;
        }
        printf("%d\n",l);
    }
    return 0;
}