python/TangDou/LuoGuBook/15_1.cpp

#include <bits/stdc++.h>

using namespace std;

//递归版本
int ans;
void play_recursion(int n) {
    ans += n;
    if (n == 1 || n == 2) return;
    play_recursion(n - 1);
    play_recursion(n - 2);
}

//利用栈的版本
int play_stack(int n) {
    //特判
    if (n == 1 || n == 2) return n;
    //栈
    stack<int> s;
    //初始化
    s.push(1);
    s.push(2);
    int sum;
    for (int i = 3; i <= n; i++) {
        int y = s.top();
        s.pop();
        int x = s.top();
        s.pop();

        sum = y + x + i;
        s.push(y);
        s.push(sum);
    }
    return s.top();
}

int main() {
    //递归版本
    for (int i = 1; i <= 10; i++) {
        ans = 0;
        play_recursion(i);
        cout << ans << " ";
    }
    cout << endl;
    //栈+循环版本
    for (int i = 1; i <= 10; i++)
        cout << play_stack(i) << " ";
    return 0;
}