美团第一题，黑白矩阵

已经一个矩阵，求将其转化为黑白矩阵的最少改变数字的次数，
input:
3 3
1 1 1
1 5 1
1 1 1
ans:4,因为
5 1 5
1 5 1
5 1 5

又有input:
3 3
1 1 1
1 1 1
1 1 1
ans:4,因为
1 2 1
2 1 2
1 2 1
我在本机上通过的代码：

import java.util.*;
import java.util.Map.Entry;

public class MainM
{
    public static void main(String args[])
    {
        Scanner cin = new Scanner(System.in);
        int R= cin.nextInt();
        int C= cin.nextInt();
        int d[][] = new int[R][C];
        int size = R*C*2/3+1;
        Map<Integer,Integer> map1 = new HashMap<Integer,Integer>(size);
        Map<Integer,Integer> map2 = new HashMap<Integer,Integer>(size);
        for(int r=0;r<R;++r) {
        	for(int c=0;c<C;++c) {
            	d[r][c] = cin.nextInt();
            	if((r+c)%2==0) {
            		if(!map1.containsKey(d[r][c]))
            			map1.put(d[r][c], 1);
            		else
            			map1.put(d[r][c], map1.get(d[r][c])+1);
            	}else {
            		if(!map2.containsKey(d[r][c]))
            			map2.put(d[r][c], 1);
            		else
            			map2.put(d[r][c], map2.get(d[r][c])+1);
            	}
            }
        }
        int ans = Integer.MAX_VALUE;
        Entry<Integer, Integer>[] en1s = getleast2( map1);
        Entry<Integer, Integer>[] en2s = getleast2( map2);
        if(en1s[0].getKey()!=en2s[0].getKey())
        	ans =R*C-en1s[0].getValue()-en2s[0].getValue();
        else
        	ans = Math.min(R*C-(en1s[1]!=null?en1s[1].getValue():0)-en2s[0].getValue() 
        			, R*C-en1s[0].getValue()-(en2s[1]!=null?en2s[1].getValue():0));
        System.out.println(ans);
    }

	private static Entry<Integer, Integer>[] getleast2(Map<Integer, Integer> map) {
		Entry<Integer, Integer>[] least2 = new Entry[2];
		for(Entry<Integer, Integer> en : map.entrySet()) {
			if(least2[0]==null)
				least2[0]=en;
			else if(least2[1]==null) {
				least2[1]=en;
				if(en.getValue()<least2[0].getValue()) {
					least2[1] = least2[0];
					least2[0] = en;
				}
			}else if(en.getValue()<least2[0].getValue()){
				least2[1] = least2[0];
				least2[0] = en;
			}else if(en.getValue()<least2[1].getValue()){
				least2[1] = en;
			}
		}
		return least2;
	}
}