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hello-algo/codes/cpp/chapter_dynamic_programming/climbing_stairs_constraint_...

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/**
* File: climbing_stairs_constraint_dp.cpp
* Created Time: 2023-07-01
* Author: Krahets (krahets@163.com)
*/
#include "../utils/common.hpp"
/* 带约束爬楼梯:动态规划 */
int climbingStairsConstraintDP(int n) {
if (n == 1 || n == 2) {
return 1;
}
// 初始化 dp 表,用于存储子问题的解
vector<vector<int>> dp(n + 1, vector<int>(3, 0));
// 初始状态:预设最小子问题的解
dp[1][1] = 1;
dp[1][2] = 0;
dp[2][1] = 0;
dp[2][2] = 1;
// 状态转移:从较小子问题逐步求解较大子问题
for (int i = 3; i <= n; i++) {
dp[i][1] = dp[i - 1][2];
dp[i][2] = dp[i - 2][1] + dp[i - 2][2];
}
return dp[n][1] + dp[n][2];
}
/* Driver Code */
int main() {
int n = 9;
int res = climbingStairsConstraintDP(n);
cout << "" << n << " 阶楼梯共有 " << res << " 种方案" << endl;
return 0;
}