70. Climbing Stairs (Easy)

https://leetcode.com/problems/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?

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

Hints

Solutions

class Solution {
    public int climbStairs(int n) {
        if (n == 0 || n == 1) return 1;
        int[] A = new int[n + 1];
        A[n] = 1;
        A[n - 1] = 1;
        for (int i = n - 2; i >= 0; i--)
            A[i] = A[i + 1] + A[i + 2];
        return A[0];
    }
}
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