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
class Solution {
public int climbStairs(int n) {
if (n <= 1) {
return 1;
}
int[] dp = new int[n];
dp[0] = 1;
dp[1] = 2;
for (int i = 2; i < n; i++) {
//当前是前一步或者前两步的方法和
dp[i] = dp[i - 1] + dp[i - 2];
}
return dp[n-1];
}
}