[LeetCode][JavaScript]Climbing Stairs

Climbing Stairs

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?

https://leetcode.com/problems/climbing-stairs/

 

 

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直接递归超时了，要动态规划。

打印前几个数就可以看出规律，1, 2, 3, 5, 8...

从3开始dp[i] = dp[i - 1] + dp[i - 2]。

 

/**
 * @param {number} n
 * @return {number}
 */
var climbStairs = function(n) {
    if(n === 0) return 0;
    if(n === 1) return 1;
    if(n === 2) return 2;
    var dp = [0, 1, 2];
    for(var i = 3; i <= n; i++)
        dp[i] = dp[i - 1] + dp[i - 2];
    return dp[n];
};