JAVA-汉诺塔

• • 思路
  • 于是有
  • 代码

这是一个经典的递归问题，递归问题的解决思路就两点：

1. 基线条件：不在调用自身
2. 递归条件：调用自身

调用自身的条件很好找，将除了最大的金盘以外的其他盘子移到中间的柱子，再将最大的盘子移动到最后一根柱子上，最后将中间的盘子全部移到最后一根柱子上。简直就是将大象移动到冰箱；

不在调用自身的条件也很简单，每一个起始柱子上的盘子移动完了就可以结束了

private void  moveTower(int height, String towerFirst, String towerMiddle, String towerLast) {
        if (height < 1) {
            return;
        }
        moveTower(height - 1, towerFirst, towerLast, towerMiddle);  // 将 n-1 个盘子移到中间柱子上
        moveDisk(height, towerFirst, towerLast);  // 将最大的盘子移到最后一个柱子上
        moveTower(height - 1, towerMiddle, towerFirst, towerLast);  // 将中间的n-1 个盘子移动到最后一个柱子上
    }

 private void moveDisk(int height, String fromTower, String toTower) {
        System.out.println((String.format("move disk %s from %s to %s", height, fromTower, toTower)));
    }

接下来就是记录每根柱子上有哪些盘子

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;

public class recursion {
    public static void main(String[] args) {
        HanoTowel hanoTowel = new HanoTowel(5, "tower1", "tower1", "tower2", "tower3");
        hanoTowel.start2move();
    }
}


class HanoTowel {
    int height;
    String tower1;
    String tower2;
    String tower3;
    static List towerFirst = new ArrayList<>();
    static List towerMiddle = new ArrayList<>();
    static List towerLast = new ArrayList<>();
    static HashMap> towers = new HashMap<>();
    public HanoTowel(int height, String hasDiskTower, String tower1, String tower2, String tower3) {
        this.height = height;
        this.tower1 = tower1;
        this.tower2 = tower2;
        this.tower3 = tower3;
        towers.put(tower1, towerFirst);
        towers.put(tower2, towerMiddle);
        towers.put(tower3, towerLast);
        for (int i = height; i > 0; i--) {
            towers.get(hasDiskTower).add(i);
        }
    }

    public void start2move(){
        moveTower(height, tower1, tower2, tower3);
    }
    
    private void  moveTower(int height, String towerFirst, String towerMiddle, String towerLast) {
        if (height < 1) {
            return;
        }
        moveTower(height - 1, towerFirst, towerLast, towerMiddle);
        moveDisk(height, towerFirst, towerLast);
        moveTower(height - 1, towerMiddle, towerFirst, towerLast);
    }

    private void moveDisk(int height, String fromTower, String toTower) {
        towers.get(toTower).add(height);
        towers.get(fromTower).remove(towers.get(fromTower).size() - 1);
        System.out.println((String.format("move disk %s from %s to %s", height, fromTower, toTower)));
        System.out.println(towers);
    }
}