面试题 08.01. 三步问题DP水题

Posted 2021-12-08 幽殇默

https://leetcode-cn.com/problems/three-steps-problem-lcci/

class Solution {
public:
    const int mod=1e9+7;
    int waysToStep(int n) 
    {
        long long int f[1000001]={0};
        f[0]=1,f[1]=1,f[2]=2;
        for(int i=3;i<=n;i++) f[i]=(f[i-1]+f[i-2]+f[i-3])%mod;
        return f[n];
    }
};