Difficulty: Easy
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
Language: Java
class Solution {
public int climbStairs(int n) {
int[] dp = new int[n + 1];
return this.climbStairs(dp, n);
}
private int climbStairs(int[] dp, int n) {
if (n <= 1) {
return 1;
}
if (dp[n] > 0) {
return dp[n];
}
int num = climbStairs(dp, n - 1) + climbStairs(dp, n - 2);
dp[n] = num;
return num;
}
}