70. Climbing Stairs
Easy
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
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 | //C++ //C++: 0ms class Solution { public: int climbStairs(int n) { if(n<=2) return n; vector<int> dp(n, 0); dp[0] = 1; dp[1] = 2; for(int i=2; i<n; ++i){ dp[i] = dp[i-2]+dp[i-1]; } return dp[n-1]; } }; //Java class Solution { public int climbStairs(int n) { int[] dp = new int[n+1]; dp[0] = 1; dp[1] = 1; for(int i=2; i<=n; ++i){ dp[i] = dp[i-1]+dp[i-2]; } return dp[n]; } } |
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