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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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// 當爬到第 n 階時，方案數量加 1
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if (state === n) res.set(0, res.get(0) + 1);
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// 走訪所有選擇
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for (const choice of choices) {
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// 剪枝：不允許越過第 n 階
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if (state + choice > n) continue;
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// 嘗試：做出選擇，更新狀態
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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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/* 爬樓梯：回溯 */
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function climbingStairsBacktrack(n) {
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const choices = [1, 2]; // 可選擇向上爬 1 階或 2 階
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const state = 0; // 從第 0 階開始爬
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const res = new Map();
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res.set(0, 0); // 使用 res[0] 記錄方案數量
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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} 階樓梯共有 ${res} 種方案`);
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