为什么我dp分还没记忆化搜索分高,求调

#include <iostream>
using namespace std;

int main() {
    int n;
    cin >> n;

    if (n==0) {
        cout <<1<< endl;
        return 0;
    }
    if (n==1) {
        cout <<1<< endl; 
        return 0;
    }
    if (n==2) {
        cout <<2<<endl; 
        return 0;
    }
    int dp[n+1];
    dp[0] = 1; 
    dp[1] = 1; 
    dp[2] = 2;

    for (int i = 3; i <= n; i++) 
        dp[i] = dp[i-1] + dp[i-2] + dp[i-3];

    cout <<dp[n]<<endl;
    return 0;
}