hello-algo/codes/javascript/chapter_dynamic_programming/climbing_stairs_backtrack.js

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/**
* File: climbing_stairs_backtrack.js
* Created Time: 2023-07-26
* Author: yuan0221 (yl1452491917@gmail.com)
*/
/* 回溯 */
function backtrack(choices, state, n, res) {
// 当爬到第 n 阶时,方案数量加 1
if (state === n) res.set(0, res.get(0) + 1);
// 遍历所有选择
for (const choice of choices) {
// 剪枝:不允许越过第 n 阶
if (state + choice > n) continue;
// 尝试:做出选择,更新状态
backtrack(choices, state + choice, n, res);
// 回退
}
}
/* 爬楼梯:回溯 */
function climbingStairsBacktrack(n) {
const choices = [1, 2]; // 可选择向上爬 1 或 2 阶
const state = 0; // 从第 0 阶开始爬
const res = new Map();
res.set(0, 0); // 使用 res[0] 记录方案数量
backtrack(choices, state, n, res);
return res.get(0);
}
/* Driver Code */
const n = 9;
const res = climbingStairsBacktrack(n);
console.log(`${n} 阶楼梯共有 ${res} 种方案`);