Interview question 3: Repeating numbers in an array

•  

• #include <iostream>
  /*
      Interview question 3: Repeating numbers in an array:
      Question: An array of length n, each element of size between 0 and n-1, find the repeated numbers in it
      Solution: 1. Sort O(nlogn)
              2. Using a hash table, the hash function maps the key key to an array subscript o(n), space complexity (n)
              3. When there are no duplicates and they are sorted, the subscript and value should be equal, so scan the array:
                      When the value there is not in its place, put it where it should be
                      When the value there is in its bit, scan the next element
                      In a word: put a value that is no longer in its place where it should be
  
  
  */
  using namespace std;
  const int MAX = 1000;
  int array_n[MAX];
  int n;
  int main(void)
  {
      cin >> n;
      for (int i = 0; i < n; i++)
          cin >> array_n[i];
  
      int i=0;
      bool find_duplicates = false;
      int duplicates = 0;
      while(true)
      {
          if(i == n)
              break;
  
          // when its bit, scan the next element 
          if (array_n[i] == i)
              i++;
          else
          {
              // Check the duplicate before swapping positions 
              if (array_n[array_n[i]] == array_n[i])
              {
                  find_duplicates = true;
                  duplicates = array_n[i];
                  break;
              }
              else
              {
                  // when not in its place, put it where it should be 
                  int temp = array_n[array_n[i]];
                  array_n[array_n[i]] = array_n[i];
                  array_n[i] = temp;
              }
          }
      }
      if (find_duplicates) cout << duplicates;
      else cout << "not find";
      return 0;
  }