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