Leetcode 70. Climbing Stairs 爬楼梯 (递归,记忆化，动态规划)

题目描述

测试样例

Input: 2
Output:  2

Explanation: 到第二阶有2种走法
1. 1 步 + 1 步
2. 2 步

Input: 3
Output:  3
Explanation:  到第三阶有3种走法
1. 1 步 + 1 步 + 1 步
2. 1 步 + 2 步
3. 2 步 + 1 步

详细分析

算法实现

class Solution {
public:
int climbStairs(int n) {
this->n = n;

memo = new int[n+2];
for(int i=0;i<n+2;i++){
memo[i] = -1;
}

return recursiveClimbing(0);
}

int recursiveClimbing(int currentStep){
if(memo[currentStep]!=-1){
return memo[currentStep];
}

if(currentStep==n){
return 1;
}
if(currentStep>n){
return 0;
}
memo[currentStep] = recursiveClimbing(currentStep+1) + recursiveClimbing(currentStep+2);
return memo[currentStep];
}
private:
int n;
int total = 0;
int *memo;
};