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问题 A: Fibonacci

草原小黄河 2022-05-02 阅读 49
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题目描述
The Fibonacci Numbers{0,1,1,2,3,5,8,13,21,34,55…} are defined by the recurrence:
F0=0 F1=1 Fn=Fn-1+Fn-2,n>=2
Write a program to calculate the Fibonacci Numbers.

输入
Each case contains a number n and you are expected to calculate Fn.(0<=n<=30) 。

输出
For each case, print a number Fn on a separate line,which means the nth Fibonacci Number.

样例输入

1

样例输出

1

思路:递归。

#include <cstdio>
#include <algorithm>
using namespace std;

const int maxn = 31;
int dp[maxn];

int F(int n) {
    if (n == 0 || n == 1) return 1;
    if (dp[n] != -1) {
        return dp[n];
    } else {
        dp[n] = F(n - 1) + F(n - 2);
        return dp[n];
    }
}

int main() {
    int n;
    fill(dp, dp + maxn, -1);
    while (scanf("%d", &n) != EOF) {
        printf("%d\n", F(n - 1));
    }
    return 0;
}
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