Finding Median of an Array - arrays

Question

I am trying to write a C program to find the median of an array, but the task requires to not sort the array. The current code I have works, but fails when there is a repeated number. I am struggling to find a way to account for this case. Any help would be appreciated.
#include <stdio.h>
#include <stdlib.h>
int median_finder(int size, int* data) {
int n1, n2;
int count = 0;
for (int t = 0; t < size; t ++) {
int piv = data[t];
int higher = 0;
int lower = 0;
int median;
if (size % 2 != 0) {
for (int j = 0; j < size; j++) {
if (piv < data[j]) {
higher++;
} else if (piv > data[j]) {
lower++;
}
}
if (higher != 0 && lower == higher) {
printf("MEDIAN: %d\n", piv);
return 0;
}
} else {
//int num = 0;
for (int j = 0; j < size; j++) {
if (piv < data[j]) {
higher++;
} else if (piv > data[j]) {
lower++;
}
}
if (higher != 0 && (lower == size/2 || higher == size/2)) {
count++;
if (count == 1) {
n1 = piv;
} if (count == 2) {
n2 = piv;
}
}
} if (count == 2) {
if (n1 > n2) {
median = n2;
} else {
median = n1;
}
printf("Median: %d\n", median);
return 0;
}
}
}
int main(int argc, char** argv) {
int size = atoi(argv[1]);
argv++;
argv++;
int data[size];
for (int i = 0; i < size; i++) {
data[i] = atoi(argv[i]);
}
median_finder(size, data);
}

Answer 1

The median for an unsorted array with possible duplicate values a of length n is the element with the value a[i] where half of the remaining elements (n-1)/2 (rounded down) are between less than (lt) or less than and equal (lt + eq) to a[i]:
#include <assert.h>
#include <stdio.h>
int median(size_t n, int *a) {
assert(n > 0);
for(size_t i = 0; i < n; i++) {
size_t lt = 0;
size_t eq = 0;
for(size_t j = 0; j < n; j++) {
if(i == j) continue;
if(a[j] < a[i]) lt++;
else if(a[j] == a[i]) eq++;
}
if((n-1)/2 >= lt && (n-1)/2 <= lt + eq)
return a[i];
}
assert(!"BUG");
}
// tap-like
void test(size_t test, int got, int expected) {
printf("%sok %zu\n", got == expected ? "" : "not ", test);
if(got != expected) {
printf(" --\n"
" got: %d\n"
" expected: %d\n"
" ...\n", got, expected);
}
}
int main(void) {
struct {
size_t n;
int *a;
} tests[] = {
{1, (int []) {0}},
{2, (int []) {0, 1}},
{3, (int []) {-1, 0, 1}},
{4, (int []) {-1, 0, 0, 1}},
};
for(int i = 0; i < sizeof tests / sizeof *tests; i++) {
test(i+1, median(tests[i].n, tests[i].a), 0);
}
}