210DaysLeetCode/day-122.cpp at master · PranjalAgni/210DaysLeetCode · GitHub

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/*
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?

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


Constraints:

1 <= n <= 45

*/

// Easy dp solution
class Solution {
   public:
    int climbStairs(int n) {
        vector<int> dp(n + 1);

        dp[0] = 1;
        dp[1] = 1;

        for (int steps = 2; steps <= n; steps++) {
            dp[steps] = dp[steps - 1] + dp[steps - 2];
        }

        return dp[n];
    }
};