(Leet Code c++)Climbing Stairs

70. Climbing Stairs

 

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

 

DP 알고리즘

class Solution {
public:
    int climbStairs(int n) {
        vector<int> ways(n + 2, 0);
        
        ways[1] = 1;
        ways[2] = 2;
        
        for(int i = 3; i <= n; i++){
            ways[i] = ways[i - 1] + ways[i - 2];
        }
        
        return ways[n];
    }
};