C++ :

#include<bits/stdc++.h>
using namespace std;
 
//定义方向增量
int dx[12]={1,1,-1,-1,2,2,-2,-2};
int dy[12]={-2,2,2,-2,1,-1,1,-1};
int s[200][200];//定义棋盘，保存到达每个步的最少步数 
char a[200][200];//棋盘 
int que[10000][4];
 
int main(){
    int n,m,i,j; 
    int s1,s2,e1,e2;//开始和结束位置 
     
    cin>>m>>n;
    for(i = 1;i <= n;i++){
        for(j = 1;j <= m;j++){
            cin>>a[i][j];
            if(a[i][j] == 'K'){
                s1 = i;
                s2 = j;
            }else if(a[i][j] == 'H'){
                e1 = i;
                e2 = j;
            }
        }
    }
     
    //初始化 
    memset(s,-1,sizeof(s));
    int head=1,tail=1;//初始化队列
    //(s1,s2)点入队,到达该点的最少步数0
    que[1][1]=s1;que[1][2]=s2;que[1][3]=0;
    while(head<=tail){
        //循环8个方向，将所能到达的点入队
        for(int i=0;i<8;i++){
            //马跳跃后的位置
            int x=que[head][1]+dx[i];
            int y=que[head][2]+dy[i];
            //如果没有越界 
            if(x>=1&&y>=1&&x<=n&&y<=m&&a[x][y]!='*'){
                //并且该点没有走过，则点入队 
                if(s[x][y]==-1){
                    s[x][y]=que[head][3]+1; //计算从(s1,s2)到(x,y)的最少步数
                    tail++;//队尾+1
                    //x,y入队
                    que[tail][1]=x;
                    que[tail][2]=y;
                    que[tail][3]=s[x][y];
                    //到达(e1,e2)的最小路径都被求出后输出 
                    if(s[e1][e2]>0){
                        cout<<s[e1][e2]<<endl;
                        return 0;//跳出循环，不再遍历 
                    }
                } 
                 
            }   
        } 
        head++;//出队
    } 
}

Java :

import java.util.LinkedList;
import java.util.Queue;
import java.util.Scanner;

public class Main {
	static int n;
	static int m;
	//起点K
	static int x;
	static int y;
	//终点H
	static int s;
	static int t;
	//记录步数
	static int a[][] = new int[151][151];
	static char map[][] = new char[151][151];
	//方向数组
	static int fx[] = {-1,-2,-2,-1,1,2,2,1};
	static int fy[] = {-2,-1,1,2,2,1,-1,-2};
	//队列
	static Queue<Node> Q = new LinkedList<Node>();
	
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		m = sc.nextInt();
		n = sc.nextInt();
		int i,j;
		String st = null;
		for(i=1;i<=n;i++) {
			st = sc.next();
			for(j=1;j<=m;j++) {
				map[i][j] = st.charAt(j-1);
				if(map[i][j]=='K'){
					x = i;
					y = j;
				}else if(map[i][j]=='H') {
					s = i;
					t = j;
				}
				a[i][j] = 99;
			}
		}
		Node now = new Node();
		Node next = new Node();
		
		//起始点赋值
		now.i = x;
		now.j = y;
		now.d = 0;
		Q.add(now);
		a[now.i][now.j] = now.d;
		//队列有元素
		while(Q.size()>0) {
			now = new Node();
			now = Q.peek();
			Q.remove();
			//方向数组遍历
			for(int k=0;k<8;k++) {
				next = new Node();
				next.i = now.i + fx[k];
				next.j = now.j + fy[k];
				next.d = now.d + 1;
				if(next.i>=1 && next.i<=n && next.j>=1 && next.j<=m && map[next.i][next.j]!='*' && next.d < a[next.i][next.j]) {
					//更新最小路径
					a[next.i][next.j] = next.d;
					Q.add(next);
				}
			}
		}
		System.out.println(a[s][t]);
		sc.close();
	}	
}

class Node{
	int i,j,d;

	@Override
	public String toString() {
		return "Node [i=" + i + ", j=" + j + ", d=" + d + "]";
	}
	
}