描述
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 0 and 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.
解析
这里的题意比较简单，就是先定义第一个和第二个数字，其他的数字按照公式计算即可。时间复杂度为 O(N)，空间复杂度为 O(N)，N 是 A 的长度。
解答
class Solution(object):
def fib(self, N):
"""
:type N: int
:rtype: int
"""
result = [0]*(N+1)
if N==0:
return result[N]
result[1]=1
if N==1:
return result[N]
for i in range(2, N+1):
result[i] = result[i-1]+result[i-2]
return result[N]
运行结果
Runtime: 20 ms, faster than 70.03% of Python online submissions for Fibonacci Number.
Memory Usage: 11.6 MB, less than 83.95% of Python online submissions for Fibonacci Number.
