70. Climbing Stairs

Description:

You are climbing a stair case. It takes n steps to reach to the top.

Each time you can either climb 1 or 2 steps. In how many distinct ways can you climb to the top?

Note: Given n will be a positive integer.

Example 1:

Input: 2
Output:  2
Explanation:  There are two ways to climb to the top.

1. 1 step + 1 step
2. 2 steps

Example 2:

Input: 3
Output:  3
Explanation:  There are three ways to climb to the top.

1. 1 step + 1 step + 1 step
2. 1 step + 2 steps
3. 2 steps + 1 step

My code:

/**
 * @param {number} n
 * @return {number}
 */
var climbStairs = function(n) {
    let num1 = 1, num2 = 2, temp = 0;
    if(n == 1 || n == 2) {
        return n;
    }
    for(let i = 3; i <= n; i++) {
        temp = num1 + num2;
        num1 = num2;
        num2 = temp;
    }
    return temp;
};

Note: 简单算一下前几个结果可以看出是斐波那契数列