剑指 Offer 10- I. 斐波那契数列

class Solution {
public:
    int fib(int n) {
        if(n<=1) return n;
        
        vector<int>dp(n+1,0);
        dp[1] = 1;
        for(int i = 2;i<=n;i++)
        {
            dp[i] = (dp[i-1]+dp[i-2])%1000000007;
        }
        return dp[n];
    }
};