C/C++ How can I get unique value from 2 arrays? - c++

Question

I need to get the unique value from 2 int arrays
Duplicate is allowed
There is just one unique value
like :
int arr1[3]={1,2,3};
int arr2[3]={2,2,3};
and the value i want to get is :
int unique[]={1}
how can i do this?
im already confused in my 'for' and 'if'
this was not homework
i know how to merge 2 arrays and del duplicate values
but i alse need to know which array have the unique value
plz help me :)
and here is some code i did
int arr1[3]={1,2,3}
int arr2[3]={2,2,3}
int arrunique[1];
bool unique = true;
for (int i=0;i!=3;i++)
{
for (int j=0;j!=3;j++)
{
if(arr1[i]==arr2[j])
{
unique=false;
continue;
}
else
{
unique=true;
}
if(unique)
{
arrunique[0]=arr1[i]
break;
}
}
cout << arrunique[0];

Answer 1

Assuming:
You have two arrays of different length,
The arrays are sorted
The arrays can have duplicate values in them
You want to get the list of values that only appear in one of the arrays
including their duplicates if present
You can do (untested):
// Assuming arr1[], arr2[], and lengths as arr1_length
int i = 0,j = 0, k = 0;
int unique[arr1_length + arr2_length];
while(i < arr1_length && j < arr2_length) {
if(arr1[i] == arr2[j]) {
// skip all occurrences of this number in both lists
int temp = arr1[i];
while(i < arr1_length && arr1[i] == temp) i++;
while(j < arr2_length && arr2[j] == temp) j++;
} else if(arr1[i] > arr2[j]) {
// the lower number only occurs in arr2
unique[k++] = arr2[j++];
} else if(arr2[j] > arr1[i]) {
// the lower number only occurs in arr1
unique[k++] = arr1[i++];
}
}
while(i < arr1_length) {
// if there are numbers still to read in arr1, they're all unique
unique[k++] = arr1[i++];
}
while(j < arr2_length) {
// if there are numbers still to read in arr2, they're all unique
unique[k++] = arr2[j++];
}
Some alternatives:
If you don't want the duplicates in the unique array, then you can skip all occurrences of this number in the relevant list when you assign to the unique array.
If you want to record the position instead of the values, then maintain two arrays of "unique positions" (one for each input array) and assign the value of i or j to the corresponding array as appropriate.
If there's only one unique value, change the assignments into the unique array to return.

Answer 2

Depending on your needs, you might also want to look at set_symmetric_difference() function of the standard library. However, its treatment of duplicate values makes its use a bit tricky, to say the least.

Answer 3

#include <stdio.h>
#include <stdlib.h>
int cmp ( const void *a , const void *b )
{
return *(int *)a - *(int *)b;
}
int main()
{
int arr1[5] = {5,4,6,3,1};
int arr2[3] = {5, 8, 9};
int unique[8];
qsort(arr1,5,sizeof(arr1[0]),cmp);
printf("\n");
qsort(arr2,3,sizeof(arr2[0]),cmp);
//printf("%d", arr1[0]);
int i = 0;
int k = 0;
int j = -1;
while (i < 5 && k < 3)
{
if(arr1[i] < arr2[k])
{
unique[++j] = arr1[i];
i++;
}
else if (arr1[i] > arr2[k])
{
unique[++j] = arr2[k];
k++;
}
else
{
i++;
k++;
}
}
//int len = j;
int t = 0;
if(i == 5)
{
for(t = k; t < 3; t++)
unique[++j] = arr2[t];
}
else
for(t = i; t < 5; t++)
unique[++j] = arr2[t];
for(i = 0; i <= j; i++)
printf("%d ", unique[i]);
return 0;
}
This is my codes,though there is a good answer .
I didn't realize the idea that know which array have the unique value.
I also think that the right answer that you chose didn't , either.

Answer 4

Here is my version of the algorithm for finding identical elements in sorted arrays on Python in C ++, it works in a similar way
def unique_array(array0 : (int), array1 : (int)) -> (int):
index0, index1, buffer = 0, 0, []
while index0 != len(array0) and index1 != len(array1):
if array0[index0] < array1[index1]:
buffer.append(array0[index0])
index0 += 1
elif array0[index0] > array1[index1]:
buffer.append(array1[index1])
index1 += 1
else:
index0 += 1; index1 += 1
buffer.extend(array0[index0 : len(array0)])
buffer.extend(array1[index1 : len(array1)])
return buffer