斐波那契数列（动态规划——递推、递归）

利用递推、递归分别实现斐波那契数列（O(n)）

/*
-------------------------------------------------
   Author:       wry
   date:         2022/3/4 15:40
   Description:  Fibonacci
-------------------------------------------------
*/

#include <bits/stdc++.h>

using namespace std;

const int MAXN = 1000+10;

int memo[MAXN];

int Fibonacci1(int i) {     //O(n)
    if (memo[i]!=-1) {
        return memo[i];
    }
    if (i<2) {
        memo[i] = i;
    }
    else {
        memo[i] = Fibonacci1(i-1) + Fibonacci1(i-2);     //递归
    }
    return memo[i];
}

int Fibonacci2(int n) {       //O(n)
    for(int i=0;i<=n;i++) {
        int answer;
        if (i<2) {
            answer = n;
        }
        else {
            answer = memo[i-1] + memo[i-2];     //递推
        }
        memo[i] = answer;
    }
    return memo[n];
}


int main() {
    memset(memo,-1,sizeof(memo));
    int n;
    while (cin >> n) {
        cout << Fibonacci1(n);
    }
    return 0;
}