每日小练：Day3

1.平方数

题目链接：平方数

先将这个数字开根号，找左右两边两个数的平方，看哪个数离这个数近

import java.util.Scanner;

public class Main{
    public static void main(String[] args){
        Scanner scanner=new Scanner(System.in);
        long x =scanner.nextLong();
        long s=(long)Math.sqrt(x);
        long s1=s*s;
        long s2=(s+1)*(s+1);
        if(x-s1<s2-x) System.out.println(s1);
        else System.out.println(s2);
   }
}

2.分组

题目链接：分组

暴力解法

import java.util.*;


public class Main{
    public static int n,m;
    public static Map<Integer,Integer> hash =new HashMap<>();
    
    public static boolean check(int x){
        int g=0;
        for(int a:hash.values()){
            g+=a/x+(a%x==0?0:1);
            
        }
        return g<=m;
    }
    public static void main(String[] args){
        Scanner scanner =new Scanner(System.in);
        n=scanner.nextInt();
        m=scanner.nextInt();
        int hmax=0;
        for(int i=0;i<n;i++){
            int x=scanner.nextInt();
            hash.put(x,hash.getOrDefault(x,0)+1);
            hmax=Math.max(hmax,hash.get(x));
            
        }
        int kinds=hash.size();
        if(kinds>m){
            System.out.println(-1);
        }else{
            for(int i=1;i<=hmax;i++){
                if(check(i)){
                    System.out.println(i);
                    break;
                }
            }
        }
    }
}

二分解法

import java.util.*;


public class Main{
    public static int n,m;
    public static Map<Integer,Integer> hash =new HashMap<>();
    
    public static boolean check(int x){
        int g=0;
        for(int a:hash.values()){
            g+=a/x+(a%x==0?0:1);
            
        }
        return g<=m;
    }
    public static void main(String[] args){
        Scanner scanner =new Scanner(System.in);
        n=scanner.nextInt();
        m=scanner.nextInt();
        int hmax=0;
        for(int i=0;i<n;i++){
            int x=scanner.nextInt();
            hash.put(x,hash.getOrDefault(x,0)+1);
            hmax=Math.max(hmax,hash.get(x));
            
        }
        int kinds=hash.size();
        if(kinds>m){
            System.out.println(-1);
        }else{
            int l=1,r=hmax;
            while(l<r){
                int mid=(l+r)/2;
                if(check(mid))
                    r=mid;
                else{
                    l=mid+1;
                }
            } 
            System.out.println(l);
        }
    }
}

希望能对大家有所帮助！！！！！