Easy
Accuracy: 62.68%
Points: 2
There are n stairs, and a person standing at the bottom wants to reach the top. The person can climb either 1 stair or 2 stairs at a time. Count the number of ways, the person can reach the top (order does not matter).
Input:
n = 4
Output:
3
Explanation:
You can reach 4th stair in 3 ways.
3 possible ways are:
1, 1, 1, 1
1, 1, 2
2, 2
Here, note that {1, 1, 2}, {1, 2, 1} and {2, 1, 1} are considered same as their order does not matter.
Input:
n = 5
Output:
3
Explanation:
You may reach the 5th stair in 3 ways.
The 3 possible ways are:
1, 1, 1, 1, 1
1, 1, 1, 2
1, 2, 2
- Your task is to complete the function countWays() which takes a single argument n and returns the answer.
O(n)
O(n)
1 <= N <= 10^6
1 <= nums[i] <= 10^9
