洛谷P1316 丢瓶盖 二分答案

洛谷P1316 丢瓶盖
二分答案
二分距离
判断能够取几个

#include <bits/stdc++.h> 
#define For(i,j,k) for(int i=j;i<=k;i++)
using namespace std ; 

const int N = 100011 ; 
int n,k,mi,mx,mid,l,r ; 
int last,sum ; 
int pos[N] ; 

inline int read() 
{
    int x = 0 , f = 1 ; 
    char ch = getchar() ; 
    while(ch<'0'||ch>'9') { if(ch=='-') f = -1 ; ch = getchar(); } 
    while(ch>='0'&&ch<='9') { x = x * 10+ch-48 ; ch = getchar(); } 
    return x * f ; 
}

inline bool check(int mid) 
{
    last = pos[ 1 ] ; 
    sum = 1 ; 
    For(i,2,n) 
        if( pos[ i ] - last >= mid ) 
            last = pos[ i ],sum++ ;  
    return sum>=k ; 
}

int main() 
{
    n = read() ; k = read() ; 
    mx = mi = pos[ 1 ] = read() ; 
    For(i,2,n) 
    {
        pos[ i ] = read() ; 
        if( mi > pos[ i ] ) mi = pos[ i ] ; 
        if( mx < pos[ i ] ) mx = pos[ i ] ; 
    }
    sort(pos+1,pos+n+1) ; 
    l = 0 ;  r = mx - mi ; 
    while( l < r ) 
    {
        mid = ( l + r+1 ) >>1 ; 
        if(check(mid)) 
            l = mid ;  
        else
            r = mid-1 ; 
    }
    printf("%d
",l) ; 
    return 0 ; 
}