找到一组数只出现一次的数

#define _CRT_SECURE_NO_WARNINGS 1
#include<stdio.h>


int main()
{
  int arr[] = { 1,2,3,4,5,1,2,3,4, };
  int sz = sizeof(arr) / sizeof(arr[0]);
  int i = 0;
  for (i = 0; i < sz; i++)
  {
    int j = 0;
    int count = 0;
    for (j = 0; j < sz; j++)
    {
      if (arr[i] == arr[j])
      {
        count++;
      }
    }
    if (count == 1)
    {
      printf("danshen:%d", arr[i]);
    }
  }


  return 0;
}