划分状态的依据是最后一步所进行的操作

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

public class Main {

    /**
     * @param args
     * @throws IOException 
     * @throws NumberFormatException 
     */
    public static void main(String[] args) throws NumberFormatException, IOException {
        // TODO Auto-generated method stub
      BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(System.in));
      int n=Integer.parseInt(bufferedReader.readLine());
      char a[]=new char [n+10];
      String pString=bufferedReader.readLine();
      for(int i=1;i<=n;i++){
          a[i]=pString.charAt(i-1);
      }
      int m=Integer.parseInt(bufferedReader.readLine());
      char b[]=new char [m+10];
       pString=bufferedReader.readLine();
      for(int i=1;i<=m;i++){
          b[i]=pString.charAt(i-1);
      }

      int f[][]=new int [n+1][m+1];
      //初始化
      f[0][0]=0;
      for(int i=1;i<=n;i++)f[i][0]=i;
      for(int i=1;i<=m;i++)f[0][i]=i;

      for(int i=1;i<=n;i++){
          for(int j=1;j<=m;j++){
              f[i][j]=Math.min(f[i][j-1], f[i-1][j])+1;
              if(a[i]==b[j]) f[i][j]=Math.min(f[i][j], f[i-1][j-1]);
              else{
                  f[i][j]=Math.min(f[i][j], f[i-1][j-1]+1);
              }
          }
      }
      System.out.println(f[n][m]);

    }

}