题解 | #跳台阶扩展问题#

#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include <stack>
#include <map>
#include <queue>
#include <cmath>
using namespace std;

int arr[23];

int main() {
    int n;
    while (scanf("%d", &n) != EOF) {
        for (int i = 1; i < 23; i++) {
            arr[i] = 0;
            if (i == 1) {
                arr[i] = 1;
            } else if (i == 2) {
                arr[i] = 2;
            } 
            else {
                for(int j = 1; j < i; j++){
                    arr[i] += arr[j]; //s[i] = s[i - 1] + s[i - 2] +....+ s[0]
                }
                arr[i] += 1;
            }
        }
        printf("%d\n", arr[n]);
    }
}