climbing-stairs.cpp

// 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?
//
// Note: Given n will be a positive integer.
//
// 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
//
//


class Solution {
public:
    int climbStairs(int n) {
        if (n <= 1) {
            return n;
        }
        int dp[n + 1];
        memset(dp, 0, sizeof(dp));
        
        dp[1] = 1;
        dp[2] = 2;
        
        for (int i = 3; i <= n; i++) {
            dp[i] = dp[i-1] + dp[i-2];
        }
        
        return dp[n];
        
    }
};