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e720aa2d24
* Sync recent changes to the revised Word. * Revised the preface chapter * Revised the introduction chapter * Revised the computation complexity chapter * Revised the chapter data structure * Revised the chapter array and linked list * Revised the chapter stack and queue * Revised the chapter hashing * Revised the chapter tree * Revised the chapter heap * Revised the chapter graph * Revised the chapter searching * Reivised the sorting chapter * Revised the divide and conquer chapter * Revised the chapter backtacking * Revised the DP chapter * Revised the greedy chapter * Revised the appendix chapter * Revised the preface chapter doubly * Revised the figures
44 lines
1.4 KiB
Java
44 lines
1.4 KiB
Java
/**
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* File: climbing_stairs_backtrack.java
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* Created Time: 2023-06-30
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* Author: Krahets (krahets@163.com)
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*/
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package chapter_dynamic_programming;
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import java.util.*;
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public class climbing_stairs_backtrack {
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/* 回溯 */
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public static void backtrack(List<Integer> choices, int state, int n, List<Integer> res) {
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// 当爬到第 n 阶时，方案数量加 1
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if (state == n)
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res.set(0, res.get(0) + 1);
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// 遍历所有选择
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for (Integer choice : choices) {
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// 剪枝：不允许越过第 n 阶
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if (state + choice > n)
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continue;
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// 尝试：做出选择，更新状态
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backtrack(choices, state + choice, n, res);
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// 回退
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}
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}
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/* 爬楼梯：回溯 */
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public static int climbingStairsBacktrack(int n) {
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List<Integer> choices = Arrays.asList(1, 2); // 可选择向上爬 1 阶或 2 阶
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int state = 0; // 从第 0 阶开始爬
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List<Integer> res = new ArrayList<>();
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res.add(0); // 使用 res[0] 记录方案数量
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backtrack(choices, state, n, res);
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return res.get(0);
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}
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public static void main(String[] args) {
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int n = 9;
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int res = climbingStairsBacktrack(n);
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System.out.println(String.format("爬 %d 阶楼梯共有 %d 种方案", n, res));
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}
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}
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