Medium Accuracy: 42.67%
Submissions: 47607 Points: 4
There are n stairs, 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 matter).
n = 4
You can reach 4th stair in 5 ways.Way 1: Climb 2 stairs at a time. Way 2: Climb 1 stair at a time.Way 3: Climb 2 stairs, then 1 stair
and then 1 stair.Way 4: Climb 1 stair, then 2 stairs
then 1 stair.Way 5: Climb 1 stair, then 1 stair and
then 2 stairs.
n = 10
There are 89 ways to reach the 10th stair.
Complete the function countWays() which takes the top stair number m as input parameters and returns the answer % 10^9+7.
Expected Time Complexity : O(n) Expected Auxiliary Space: O(1)