Climbing Stairs
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. class Solution { public: int climbStairs(int n) { if (n == 0) return 0; if (n == 1) return 1; // dp space complexity is O(n) vector<int> dp(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 ]; } };