【Noip模拟 20160929】选数

#include<bits/stdc++.h>
using namespace std;
#define RE register int
#define IL inline
#define N 100001
int n,k,a[N],minn=1e9,maxx;
inline char gc(){
    static char buf[100001],*p1=buf,*p2=buf;
    return p1==p2&&(p2=(p1=buf)+fread(buf,1,100001,stdin),p1==p2)?EOF:*p1++;
}template<class T>inline int read(T&x){
    x=0;register char c=gc();
    while(c<48)c=gc();
    while(c>47)x=(x<<1)+(x<<3)+(c^48),c=gc(); 
}void write(RE x){
    if (x>9)write(x/10);
    putchar(x%10^48);
}inline int check(RE x){
    RE sum=1,temp=a[1];
    for (RE i=2;i<=n;++i)
        if (a[i]>=temp+x) sum++,temp=a[i];
    return sum>=k;
}signed main(){
    freopen("choose.in","r",stdin),freopen("choose.out","w",stdout);
    cin>>n>>k;
    for (RE i=1;i<=n;++i) cin>>a[i],maxx=max(maxx,a[i]),minn=min(minn,a[i]);
    sort(a+1,a+n+1);
    RE r=maxx,l=minn,m,ans=0;
    while(l<=r) check(m=(l+r)>>1)?ans=m,l=m+1:r=m-1;
    write(ans);
    return 0;
}