An array has only one occurrence in addition to two elements, all of the other elements appear two times, please find only one occurrence of the two elements, and output

#include <stdio.h>
#define N 10
int main ()
{
int A[n] = {1,2,7,99,3,3,4,1,2,4}, Flat[n] = {0};
int I, j, sum = a[0], last_bit = 0, SUM0 = 0, sum1 = 0;
To vary or manipulate all elements in an array
If only one element of an array appears once, the result of an XOR is that the element appears only once
for (i = 1; i < N; i + +)
{
sum = sum ^ (a[i]);
}
If there are two elements in the array that occur only once, the result of the above XOR is converted to binary and judged from right to left, and the first position of 1 is recorded as I
for (i = 0; Last_bit! = 1; i + +)
{
Last_bit = sum & 1;
sum = sum >> 1;
}
The second bit of the binary form of all the elements is then scanned, and the results are recorded in the flat array
The flat[j]=1 indicates that the first bit of the J element is 1, otherwise 0
for (j = 0; J < N; J + +)
{
FLAT[J] = (A[j] >> (i-1)) & 1;
}
Group all elements according to the flat array obtained from the above loop
The result is 1 of the different or operation together, for 0 of the different or operation, two sets of different or the result is two appear only once the element
for (j = 0; J < N; J + +)
{
(Flat[j] = = 1)? (sum1 = sum1 ^ (a[j])): (SUM0 = sum0 ^ (a[j]));
}
printf ("%d%d\n", SUM0, SUM1);
return 0;
}