zoukankan      html  css  js  c++  java
  • 509. Fibonacci Number

    The Fibonacci numbers, commonly denoted F(n) form a sequence, called the Fibonacci sequence, such that each number is the sum of the two preceding ones, starting from 0and 1. That is,

    F(0) = 0,   F(1) = 1
    F(N) = F(N - 1) + F(N - 2), for N > 1.
    

    Given N, calculate F(N).

    Example 1:

    Input: 2
    Output: 1
    Explanation: F(2) = F(1) + F(0) = 1 + 0 = 1.
    

    Example 2:

    Input: 3
    Output: 2
    Explanation: F(3) = F(2) + F(1) = 1 + 1 = 2.
    

    Example 3:

    Input: 4
    Output: 3
    Explanation: F(4) = F(3) + F(2) = 2 + 1 = 3.
    

    Note:

    0 ≤ N ≤ 30.

    M1: recursion, time = O(2^n), space = O(n)

    M2: dp, time = O(n), space = O(1)

    class Solution {
        public int fib(int N) {
            if(N <= 1) {
                return N;
            }
            int f0 = 0, f1 = 1, f2 = f0 + f1;
            for(int i = 1; i < N; i++) {
                f2 = f0 + f1;
                f0 = f1;
                f1 = f2;
            }
            return f2;
        }
    }
  • 相关阅读:
    Kefa and Park
    分土地
    果园里的树
    分解质因数
    素数筛
    cantor的数表
    new一个二维数组
    基础练习 十六进制转八进制
    查函数功能
    concatenate函数
  • 原文地址:https://www.cnblogs.com/fatttcat/p/11103082.html
Copyright © 2011-2022 走看看