hello-algo/codes/rust/chapter_dynamic_programming/climbing_stairs_backtrack.rs
Yudong Jin e720aa2d24
feat: Revised the book (#978)
* 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
2023-12-02 06:21:34 +08:00

37 lines
1.1 KiB
Rust

/*
* File: climbing_stairs_backtrack.rs
* Created Time: 2023-07-09
* Author: sjinzh (sjinzh@gmail.com)
*/
/* 回溯 */
fn backtrack(choices: &[i32], state: i32, n: i32, res: &mut [i32]) {
// 当爬到第 n 阶时,方案数量加 1
if state == n { res[0] = res[0] + 1; }
// 遍历所有选择
for &choice in 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 */
fn climbing_stairs_backtrack(n: usize) -> i32 {
let choices = vec![ 1, 2 ]; // 可选择向上爬 1 阶或 2 阶
let state = 0; // 从第 0 阶开始爬
let mut res = Vec::new();
res.push(0); // 使用 res[0] 记录方案数量
backtrack(&choices, state, n as i32, &mut res);
res[0]
}
/* Driver Code */
pub fn main() {
let n: usize = 9;
let res = climbing_stairs_backtrack(n);
println!("{n} 阶楼梯共有 {res} 种方案");
}