How to solve this question?

A farmer wants to reorganize the crops growing in his farm. The farm is in the form of an N X M grid with each cell in the grid being a square plot. Each plot has to be planted with a variety of crop. The farmer has 26 varieties of crops that he can plant. The plant varieties are represented by lowercase English alphabets.

He wants to follow the following condition while planting:

  • In each row, there must be at least 2 different varieties of crops ( any number of crops can be used in a column)
  • No two nearby (Top, bottom, left, right) plots can have the same variety of crops.

Given the current state of the farm, find the minimum number of plots that have to replant with a different crop so that the above conditions are satisfied.

Input:
The first line contains two integers N and M, the dimensions of the farm.The next N lines contain M lowercase characters from‘a’ to ‘z’ representing the crop variety at that plot.
Output:
Output a single integer denoting the minimum number of plots that have to be replanted in order to satisfy the conditions imposed.

Example 1
input:
4 4
acaa
dddd
bbbb
ccce

Output: 6
Explanation: In this Example, We may replant the farm to look like:
acac
dede
baba
cece
This arrangement of crop varieties satisfies the given conditions and the cost of this replacement is 6.

code snippet:

import java.util.Scanner;
class Solution {
public static void main(String[] args)
{

   int n;
   Scanner in = new Scanner(System.in);
   n = in.nextInt();
   in.nextLine();
   String[] crops = new String[n];
   for (int i=0;i<n;i++){
   crops[i]=in.nextLine().trim();
   }
   System.out.print(replant(crops));
}

public static int replant(String[] crops){
   // Write your code here
   // Return the number of replanted crops
   return 0;
   }
}