How to find out if the largest rectangle contains other rectangles inside - c

Question

It is necessary to create N rectangles using two upper left and bottom right points. Then find the area of the largest rectangle (rectangle with the largest area = biggest rectangle) and determine whether other rectangles are inside the largest one if not, then display the appropriate message.
I've already have code which generates N rectangles and determines the largest area among them, but the main problem is to find out if there are smaller rectangles in the biggest one.
Let's simulate the situation:
Rectangle 1 A - (topLeft.x topLeft.y) , B - (botRight.x botRight.y)
Rectangle 2 C - (topLeft.x topLeft.y) , D - (botRight.x botRight.y)
If a rectangle contains another rectangle, then
A(y)>C(y) && A(x)<C(x) && B(y)<D(y) && B(x)>D(y)
Looks easy, but how to implement this algorithm for 20 rectangles, for instance?
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#define N 20
struct Point {
int x;
int y;
};
struct Rectangle {
struct Point topLeft;
struct Point botRight;
int area;
};
int Area(const struct Rectangle* r)
{
int length, breadth;
length = r->botRight.x - r->topLeft.x;
if (length <= 0)
exit(1);
breadth = r->topLeft.y - r->botRight.y;
if (breadth <= 0)
exit(2);
return length * breadth;
}
int genRec(struct Rectangle* rec);
int main(void)
{
srand(time(NULL));
int maxarea = 0;
int maxidx = 0;
struct Rectangle rec[N];
for (int i = 0; i < N; i++) {
printf("\n");
printf("\t----------RECTANGLE %d----------\n", i + 1);
int area = genRec(&rec[i]);
if (area > maxarea) {
maxarea = area;
maxidx = i;
}
}
printf("\n");
printf("\tMaximum area is %d in Rectangle %d\n", maxarea, maxidx + 1);
return 0;
}
void genPair(int* lo, int* hi)
{
while (1) {
*lo = -50 + rand() % 101;
*hi = -50 + rand() % 101;
if (*lo < *hi)
break;
}
}
int genRec(struct Rectangle* rec)
{
genPair(&rec->topLeft.x, &rec->botRight.x);
genPair(&rec->botRight.y, &rec->topLeft.y);
printf("\tTop left point is x = %d y = %d\n",
rec->topLeft.x, rec->topLeft.y);
printf("\tBottom right point is x = %d y = %d\n",
rec->botRight.x, rec->botRight.y);
int area = Area(rec);
printf("\tArea is %d\n", area);
return area;
}