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;
}