LeetCode 70. Climbing Stairs

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

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