LeetCode-in-All
70. Climbing Stairs
Easy
You are climbing a staircase. It takes n steps to reach the top.
Each time you can either climb 1 or 2 steps. In how many distinct ways can you climb to the top?
Example 1:
Input: n = 2
Output: 2
Explanation: There are two ways to climb to the top. 1. 1 step + 1 step 2. 2 steps
Example 2:
Input: n = 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
Constraints:
1 <= n <= 45
Solution
public class Solution {
public int ClimbStairs(int n) {
int[] dp = new int[n + 1];
dp[0] = 1;
for (int i = 0; i < dp.Length; i++) {
if (i + 1 < dp.Length) {
dp[i + 1] += dp[i];
}
if (i + 2 < dp.Length) {
dp[i + 2] += dp[i];
}
}
return dp[dp.Length - 1];
}
}