70. Climbing Stairs

https://leetcode.com/problems/climbing-stairs/

Problem

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

Solution

class Solution {
public:
    int climbStairs(int n) {
        if (n == 0 || n == 1) return 1;
        const int size = n + 1;
        int dp[size];
        dp[0] = dp[1] = 1;
        for (int i = 2; i < size; ++i) dp[i] = 0;
        for (int i = 2; i < size; ++i) dp[i] = dp[i - 1] + dp[i - 2];
        return dp[n];
    }
};

• #dp