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35 lines
1002 B
35 lines
1002 B
/**
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* File: climbing_stairs_backtrack.js
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* Created Time: 2023-07-26
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* Author: yuan0221 (yl1452491917@gmail.com)
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*/
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/* 回溯 */
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function backtrack(choices, state, n, 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) res.set(0, res.get(0) + 1);
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// 遍历所有选择
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for (const choice of choices) {
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// 剪枝：不允许越过第 n 阶
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if (state + choice > n) 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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function climbingStairsBacktrack(n) {
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const choices = [1, 2]; // 可选择向上爬 1 阶或 2 阶
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const state = 0; // 从第 0 阶开始爬
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const res = new Map();
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res.set(0, 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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/* Driver Code */
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const n = 9;
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const res = climbingStairsBacktrack(n);
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console.log(`爬 ${n} 阶楼梯共有 ${res} 种方案`);
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