最大和

错误

#include<bits/stdc++.h>
using namespace std;
const int N = 1e6;
int isprime[1000005] = {};
int d(int t)//最小质因数
{
  
  for (int i = 1; i <= N; i++)//最大就是自己本身
    {
        isprime[i] = i;
    }
    for (int i = 3; i < sqrt(N); i+=2)//抓奇数
    {
    for (int j = i * 2; j <= N; j += i)
    {
      if (isprime[j]>i)//使得i是最小的
      {
        isprime[j] = i;
      }
    }
    }
  if (t % 2 == 0)//偶数最小因子一定是2 
  {
    return 2;
  }
  else
  {
    return isprime[t];
  }
}
int main()
{
  int n,ans=0,square[10001],dp[10001];
  cin>>n;
  for(int i=1;i<=n;i++)
    cin>>square[i];
  for(int i=1;i<=n;i++)
  {
    if(i+1<=n)
    {
      dp[i+1]=max(dp[i+1],dp[i]+square[i+1]);
      if(dp[i+1]>ans)
      {
          ans=dp[i+1];
      }
    }
    if(i+d(n-i)<=n)
    {
      dp[i+d(n-i)]=max(dp[i+d(n-i)],dp[i]+square[i+d(n-i)]);
      if(dp[i+d(n-i)]>ans)
      {
          ans=dp[i+d(n-i)];
      }
    }
  }
  cout<<ans;
  return 0;
}

通过

#include <iostream>
#include <cstdio>
#include <string>
#include <vector>
#include <cstdlib>
#include <cstring>
#include <queue>
#include <cmath>
#include <algorithm>
using namespace std;
const int MIND = -2000000000;
int n, a[10003];
int D[10003];
int f[10003];

void getD() {
    D[1] = 1;
    for (int i = 2; i <= 10000; i++) {
        int isfind = 0;
        for (int j = 2; j*j <= i; j++) {
            if (i % j == 0) {
                D[i] = j; // 最小质因数
                isfind = 1;
                break;
            }
        }
        if (!isfind) {
            // is a prime
            D[i] = i;
        }
    } 
}

void solve() {
    f[1] = a[1];
    for (int i = 1; i <= n; i++) {
        int end = D[n-i];
        for (int j = 1; j <= end; j++) {
            if (i + j > n) break;
            f[i+j] = max(f[i+j], f[i]+a[i+j]);
        }
    }
    cout << f[n];
}

int main() {
    // codes here
    cin >> n;
    for (int i = 1; i <= n; i++) {
        cin >> a[i];
        f[i] = MIND;
    }
    
    getD();
    solve();
    return 0;
}