Lintcode Python Entry-level topic Fibonacci sequence

Description of the original title:

Finds the nth number in the Fibonacci sequence.

The so-called Fibonacci sequence refers to:

• The first 2 numbers are 0 and 1.
• The number of I is the number I-1 and the number I-2.

The first 10 digits of the Fibonacci sequence are:

0, 1, 1, 2, 3, 5, 8, 13, 21, 34 ...

Topic Analysis:

The beginning of the idea, by recursively implementing output fib (n-1) +fib (n-2) value calculation, the principle is correct, the algorithm is high complexity, resulting in a running time exceeding the Lintcode limit:

Class solution:    # @param n:an integer    # @return an integer f (n)    # recursive implementation    def Fibonacci (self, N):        If n = = 1:            return 0        elif n = = 2:            return 1        else:            return Self.fibonacci (n-1) + Self.fibonacci (n-2)

Modified to an iterative implementation, the Fibonacci number is saved to the list, loop n-2 times, each time the last element of the sequence [-1] and the penultimate element [-2] is added to the list, and finally return to the last element of the list ~

Class solution:    # @param n:an integer    # @return an integer f (n)   # implement    def Fibonacci (self, n) through the For loop iteration:        num = [0,1]        if n = = 1:            return 0        elif n ==1:            return 1 for I in        Range (0,n-2):            num.append (Num[-1] + num[-2])        return Num[-1]

　　

　　

Lintcode Python Entry-level topic Fibonacci sequence