how to remove duplicates from the array

Question

I have multiple arrays and I need to return the value of the order the customer enters, the arrays have duplicated values so even after sorting them from low to high when the order is placed he'll take the duplicated value. how can I remove the duplicated? ex. int testA1[] = { 25000, 20000, 29499, 10000, 20000, 29000, 25000, 20000, 25000, 10000 }; int order1 = 3; <-- it should print out 29000but instead it prints 25000

#include<stdio.h>

int lowestPrice(int array[], int size, int order){
    int tempArray[size];
    
    for (size_t i = 0; i < size; i++)
        tempArray[i] = array[i];

    for (size_t i = 0; i < size; i++)
        for (size_t j = i; j < size; j++)
            if (tempArray[j] < tempArray[i]) {
                int tmp = tempArray[i];
                tempArray[i] = tempArray[j];
                tempArray[j] = tmp;
            }

    int j = 0;
    for (size_t i = 0; i < size -1; i++){
        if(tempArray[i] != tempArray[i+1])
        {
            tempArray[j] = tempArray[i];                
            j++;    
        } 
        tempArray[j] = tempArray[i-1];
    }   
       
    if(order > size || order < 0){
        return -1;
    }
    else{
        return tempArray[order];    
    }
}

Answer 1

main(void){
int testA1[] = { 25000, 20000, 29499, 10000, 20000, 29000, 25000, 20000 , 25000 , 10000 };
int size = sizeof(testA1) / sizeof(int); //size of array
// if your orders are only going to be positive numbers as it should for your wealth :
// (change duplicate value by -1)
for (int i = 0; i < size ; ++i)
{
    int is_duplicate = testA1[i];
    if (is_duplicate == -1)
        continue ;
    int j = i +1;
    while ( j < size) {
        if (is_duplicate == testA1[j])
            testA1[j] = -1;
        ++j;
    }
}
// sort it ;) :
    for (size_t i = 0; i < size; i++)
        for (size_t j = i; j < size; j++)
            if (testA1[j] < testA1[i]) {
                int tmp = testA1[i];
                testA1[i] = testA1[j];
                testA1[j] = tmp;
            }
    int new_index = 0;
    while (testA1[new_index] == -1)
        ++new_index;
// here is for you to see the new state (you can remove this part)
    for (int i = new_index; i < size; ++i)
        printf("%d\n", testA1[i]);
// now get your order price from the new index (index + your_desired_value) 
    return testA1[new_index + -->your_desired_value<--];
}