Check if four segments form a rectangle

We are given four segments as a pair of coordinates of their end points. We need to tell whether those four line segments make a rectangle or not.
Examples:

```Input : segments[] =  [(4, 2), (7, 5),
(2, 4), (4, 2),
(2, 4), (5, 7),
(5, 7), (7, 5)]
Output : Yes
Given these segment make a rectangle of length 3X2.

Input : segment[] = [(7, 0), (10, 0),
(7, 0), (7, 3),
(7, 3), (10, 2),
(10, 2), (10, 0)]
Output : Not
These segments do not make a rectangle.

Above examples are shown in below diagram.

```

This problem is mainly an extension of How to check if given four points form a square

Recommended: Please solve it on “PRACTICE ” first, before moving on to the solution.

We can solve this problem by using properties of a rectangle. First, we check total unique end points of segments, if count of these points is not equal to 4 then the line segment can’t make a rectangle. Then we check distances between all pair of points, there should be at most 3 different distances, one for diagonal and two for sides and at the end we will check the relation among these three distances, for line segments to make a rectangle these distance should satisfy Pythagorean relation because sides and diagonal of rectangle makes a right angle triangle. If they satisfy mentioned conditions then we will flag polygon made by line segment as rectangle otherwise not.

```//  C++ program to check whether it is possible
// to make a rectangle from 4 segments
#include <bits/stdc++.h>
using namespace std;
#define N 4

//  structure to represent a segment
struct Segment
{
int ax, ay;
int bx, by;

Segment(int ax, int ay, int bx, int by) :
ax(ax), ay(ay), bx(bx), by(by)
{}
};

// Utility method to return square of distance
// between two points
int getDis(pair<int, int> a, pair<int, int> b)
{
return (a.first - b.first)*(a.first - b.first) +
(a.second - b.second)*(a.second - b.second);
}

// method returns true if line Segments make
// a rectangle
bool isPossibleRectangle(Segment segments[])
{
set< pair<int, int> > st;

// putiing all end points in a set to
// count total unique points
for (int i = 0; i < N; i++)
{
st.insert(make_pair(segments[i].ax, segments[i].ay));
st.insert(make_pair(segments[i].bx, segments[i].by));
}

// If total unique points are not 4, then
// they can't make a rectangle
if (st.size() != 4)
return false;

//  dist will store unique 'square of distances'
set<int> dist;

//  calculating distance between all pair of
// end points of line segments
for (auto it1=st.begin(); it1!=st.end(); it1++)
for (auto it2=st.begin(); it2!=st.end(); it2++)
if (*it1 != *it2)
dist.insert(getDis(*it1, *it2));

// if total unique distance are more than 3,
// then line segment can't make a rectangle
if (dist.size() > 3)
return false;

// copying distance into array. Note that set maintains
// sorted order.
int distance[3];
int i = 0;
for (auto it = dist.begin(); it != dist.end(); it++)
distance[i++] = *it;

// If line seqments form a square
if (dist.size() == 2)
return (2*distance[0] == distance[1]);

//  distance of sides should satisfy pythagorean
// theorem
return (distance[0] + distance[1] == distance[2]);
}

//  Driver code to test above methods
int main()
{
Segment segments[] =
{
{4, 2, 7, 5},
{2, 4, 4, 2},
{2, 4, 5, 7},
{5, 7, 7, 5}
};

if (isPossibleRectangle(segments))
cout << "Yes";
else
cout << "No";
}
```

Output:

```Yes
```

This article is contributed by Utkarsh Trivedi. If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.

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