PAT 1096 Consecutive Factors

1096 Consecutive Factors (20分)

Among all the factors of a positive integer N, there may exist several consecutive numbers. For example, 630 can be factored as 3×5×6×7, where 5, 6, and 7 are the three consecutive numbers. Now given any positive N, you are supposed to find the maximum number of consecutive factors, and list the smallest sequence of the consecutive factors.

Input Specification:

Each input file contains one test case, which gives the integer N (1<N<231).

Output Specification:

For each test case, print in the first line the maximum number of consecutive factors. Then in the second line, print the smallest sequence of the consecutive factors in the format ​​factor[1]*factor[2]*...*factor[k]​​, where the factors are listed in increasing order, and 1 is NOT included.

Sample Input:

630

Sample Output:

3
5*6*7

 又是一道感觉之前写过的题。

这道题有点考思维

直接暴力咯

之前搁置了很久没有写……？为什么呢

#include <bits/stdc++.h>
#define ll long long
using namespace std;
bool isPrime(ll a){
  for(int i = 2; i <= sqrt(a); i++){
    if(a % i == 0) return false;
  }
  return true;
}
int main(){
  ll n;
  cin >> n;
  if(isPrime(n)){
    cout << "1" << endl << n << endl;
  }else {
    int maxx = -1, j, ind;
    for(int i = 2; i <= sqrt(n); i++){
      ll sum = 1;
      for(j = 0; ; j++){
        sum *= (i+j);
//        cout << "---> " << sum << endl;
        if(n % sum != 0) break;
      }
      if(j > maxx) {
        maxx = j;
        ind = i;
      }
    }
    cout << maxx << endl;
    cout << ind;
    for(int i = 1; i < maxx; i++){
      cout << "*" << ind+i;
    }
    cout << endl;
  }
  return 0;
}