You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
37 lines
1.1 KiB
37 lines
1.1 KiB
/*
|
|
* 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 { break; }
|
|
// 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 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!("爬 {n} 阶楼梯共有 {res} 种方案");
|
|
} |