LeetCode - Fibonacci Number

문제 설명

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.

Example 1

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

Example 2

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

Example 3

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

Constraints

• 0 <= n <= 30

Solution

/**
 * @param {number} n
 * @return {number}
 */

// 재귀로 풀기
let fib2 = function(n) {
    
    if(n==0){
        return 0;
    }
    else if(n==1){
        return 1;
    }
    else{
        return fib(n-1)+fib(n-2);
    }
};


//반복문으로 풀기
let fib = function(n) {
    
    if(n==0){
        return 0;
    }
    else if(n==1){
        return 1;
    }
    else{
        let preVal=1;
        let prepreVal=0;
        let nowVal=1;
       for(let i=2; i<=n; i++ ){
        nowVal=preVal+prepreVal;
        prepreVal=preVal;
        preVal=nowVal;
       }
       return nowVal;
    }
};

처음에 재귀로 풀었다가 TC가 좋지 않아서 반복문으로 바꿔 풀어봄

~.~