POJ 3258 River Hopscotch

#include <stdio.h>
#include <string.h>
#include <iostream>
#include <algorithm>

using namespace std;

const int MAX = 50010;
int a[MAX],ans,l,n,m;

bool check(int mid){
    int last = 0,cnt = 0;//last记录上一个没有被删除的石头的id
    for(int i=1; i<=n+1; i++){
        if(a[i] - a[last] < mid)    cnt++;//如果石头之间的距离小于我们的答案，那么将这个石头删除
        else    last = i;//否则i就是没有被删除的石头标号，用last记录下来
    }
    return cnt <= m;
}

int main(){
//    freopen("in.txt", "r", stdin);
    scanf("%d%d%d",&l,&n,&m);
    for(int i=1; i<=n; i++)
        scanf("%d",&a[i]);
    a[n+1] = l;
    sort(a+1, a+1+n);
    int left = 0, right = l;
    while(left <= right){//二分枚举答案过程
        int mid = (left + right) >> 1;
        if(check(mid)){
            ans = mid;
            left = mid + 1;
        }
        else right = mid - 1;
    }
    printf("%d\n",ans);
    return 0;
}