How can I make my Code work on Larger Inputs - c

Question

I'm trying to solve the hacker rank question "Small triangle, Large triangle"
I have to arrange triangle by increasing order of area
the code I wrote is working fine on smaller input given by me but fails on the larger inputs, after taking inputs I just get terminated
eg,
working on input
3
7 24 25
5 12 13
3 4 5
not working when
10
67 67 19
3 57 55
33 33 49
61 58 59
23 43 35
48 42 45
23 12 27
41 34 22
26 49 35
63 46 45
unable to understand why!! Thank YOU!! in advance
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
struct triangle
{
int a;
int b;
int c;
};
typedef struct triangle triangle;
void sort_by_area(triangle *tr, int n)
{
int *p = (int*)malloc(n * sizeof(int));
int *middle = (int*)malloc((3*n)*sizeof(int));
// doing sum of side of triangle
for (int i = 0; i < n; i++)
{
p[i] = tr[i].a + tr[i].b + tr[i].c;
}
// arranging sum in increasing order
// as more the sum of a+b+c more its area in herons formula
for (int i = 0; i < n; i++)
{
for (int j = 0; j < n; j++)
{
if (p[i] < p[j])
{
int temp;
temp = p[i];
p[i] = p[j];
p[j] = temp;
}
}
}
int num = 0;
// storing sides in increasing order in middle
for (int i = 0; i < n; i++)
{
for (int j = 0; j < n; j++)
{
if (p[i] == tr[j].a + tr[j].b + tr[j].c)
{
middle[num] = tr[j].a;
num++;
middle[num] = tr[j].b;
num++;
middle[num] = tr[j].c;
num++;
}
}
}
num=0;
// copying increassed order in tr poiinter in question
for (int i = 0; i < n; i++)
{
tr[i].a = middle[num];
num++;
tr[i].b = middle[num];
num++;
tr[i].c = middle[num];
num++;
}
}
int main()
{
int n;
scanf("%d", &n);
triangle *tr = malloc(n * sizeof(triangle));
for (int i = 0; i < n; i++) {
scanf("%d%d%d", &tr[i].a, &tr[i].b, &tr[i].c);
}
sort_by_area(tr, n);
for (int i = 0; i < n; i++) {
printf("%d %d %d\n", tr[i].a, tr[i].b, tr[i].c);
}
return 0;
}

Answer 1

It's kind of strange that your function is called sort_by_area but it doesn't seem to calculate any area. Instead it seems to calculate the perimeter of the triangles.
Anyway... there is a bug here. (note: There may be other bugs but to start with you need to fix this)
int *middle = (int*)malloc((3*n)*sizeof(int));
...
...
int num = 0;
// storing sides in increasing order in middle
for (int i = 0; i < n; i++)
{
for (int j = 0; j < n; j++)
{
if (p[i] == tr[j].a + tr[j].b + tr[j].c)
{
middle[num] = tr[j].a;
num++;
middle[num] = tr[j].b;
num++;
middle[num] = tr[j].c;
num++;
}
}
}
You have two nested loops going from 0 to n. When the if statement is true, you increment num 3 times.
So in case p[i] == tr[j].a + tr[j].b + tr[j].c is always true (which is possible), you end up with num being equal to 3*n*n.
And you use num as index into middle but middle is only allocated to hold 3*n integers.
So you are writing outside the allocated area. That's undefined behavior.
BTW
When sorting arrays in C you should nearly always use qsort