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/**
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* File: hanota.java
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* Created Time: 2023-07-17
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* Author: krahets (krahets@163.com)
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*/
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package chapter_divide_and_conquer;
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import java.util.*;
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public class hanota {
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/* 移动一个圆盘 */
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static void move(List<Integer> src, List<Integer> tar) {
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// 从 src 顶部拿出一个圆盘
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Integer pan = src.remove(src.size() - 1);
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// 将圆盘放入 tar 顶部
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tar.add(pan);
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}
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/* 求解汉诺塔问题 f(i) */
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static void dfs(int i, List<Integer> src, List<Integer> buf, List<Integer> tar) {
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// 若 src 只剩下一个圆盘,则直接将其移到 tar
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if (i == 1) {
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move(src, tar);
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return;
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}
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// 子问题 f(i-1) :将 src 顶部 i-1 个圆盘借助 tar 移到 buf
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dfs(i - 1, src, tar, buf);
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// 子问题 f(1) :将 src 剩余一个圆盘移到 tar
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move(src, tar);
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// 子问题 f(i-1) :将 buf 顶部 i-1 个圆盘借助 src 移到 tar
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dfs(i - 1, buf, src, tar);
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}
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/* 求解汉诺塔问题 */
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static void solveHanota(List<Integer> A, List<Integer> B, List<Integer> C) {
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int n = A.size();
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// 将 A 顶部 n 个圆盘借助 B 移到 C
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dfs(n, A, B, C);
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}
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public static void main(String[] args) {
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// 列表尾部是柱子顶部
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List<Integer> A = new ArrayList<>(Arrays.asList(5, 4, 3, 2, 1));
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List<Integer> B = new ArrayList<>();
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List<Integer> C = new ArrayList<>();
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System.out.println("初始状态下:");
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System.out.println("A = " + A);
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System.out.println("B = " + B);
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System.out.println("C = " + C);
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solveHanota(A, B, C);
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System.out.println("圆盘移动完成后:");
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System.out.println("A = " + A);
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System.out.println("B = " + B);
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System.out.println("C = " + C);
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}
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}
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