爬楼梯

[Pcjmy]

[Li Xiangyue]

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