dp问题 难度：easy

Question

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
来源：力扣（LeetCode）

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Answer

class Solution {

public int climbStairs(int n) {

    if(n<=2){

    return n;

    }

    int [] dp = new int[n];

    dp[0] = 1;

    dp[1] = 2;

    for(int i = 2;i < n;i++){

        dp[i] = dp[i-1] + dp[i-2];

    }

    return dp[n-1];

    }

}