Leetcode_70

#include <iostream>
#include <vector>
#include <cassert>

using namespace std;

/// Memory Search
/// Time Complexity: O(n)
/// Space Complexity: O(n)
class Solution {

private:
    vector<int> memo;

    int calcWays(int n){

        if(n == 0 || n == 1)
            return 1;

        if(memo[n] == -1)
            memo[n] = calcWays(n - 1) + calcWays(n - 2);

        return memo[n];
    }

public:
    int climbStairs(int n) {
        assert(n > 0);
        memo = vector<int>(n + 1, -1);
        return calcWays(n);
    }
};

int main() {

    cout << Solution().climbStairs(38) << endl;

    return 0;
}

这里注意保存已经计算过的值，不然提交leetcode会超时