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.
40 lines
966 B
40 lines
966 B
/**
|
|
* File: climbing_stairs_backtrack.dart
|
|
* Created Time: 2023-08-11
|
|
* Author: liuyuxin (gvenusleo@gmail.com)
|
|
*/
|
|
|
|
/* 回溯 */
|
|
void backtrack(List<int> choices, int state, int n, List<int> res) {
|
|
// 当爬到第 n 阶时，方案数量加 1
|
|
if (state == n) {
|
|
res[0]++;
|
|
}
|
|
// 遍历所有选择
|
|
for (int 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 */
|
|
int climbingStairsBacktrack(int n) {
|
|
List<int> choices = [1, 2]; // 可选择向上爬 1 或 2 阶
|
|
int state = 0; // 从第 0 阶开始爬
|
|
List<int> res = [];
|
|
res.add(0); // 使用 res[0] 记录方案数量
|
|
backtrack(choices, state, n, res);
|
|
return res[0];
|
|
}
|
|
|
|
/* Driver Code */
|
|
void main() {
|
|
int n = 9;
|
|
|
|
int res = climbingStairsBacktrack(n);
|
|
print("爬 $n 阶楼梯共有 $res 种方案");
|
|
}
|