Question

link

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?

Stats

Frequency 5
Difficulty 2
Adjusted Difficulty 1
Time to use --------

Ratings/Color = 1(white) 2(lime) 3(yellow) 4/5(red)

Analysis

This is an easy DP question.

Solution

My code is simple and concise, better than any other.

So I posted it below.

My code

Original code

public int climbStairs(int n) {
    if (n == 1) return 1;
    if (n == 2) return 2;
    int a = 1;
    int b = 2;
    int sum = 0;
    for (int i=3 ; i<=n ; i++){
        sum = a + b;
        a = b;
        b = sum;
    }
    return sum;
}

Optimized code

public int climbStairs(int n) {
    if (n == 1) return 1;
    int a = 1;
    int sum = 1;
    for (int i=2 ; i<=n ; i++){
        sum += a;
        a = sum - a;
    }
    return sum;
}