This is a C++ Program to find the area of ploygon using slicker algorithm. The algorithm assumes the usual mathematical convention that positive y points upwards. In computer systems where positive y is downwards (most of them) the easiest thing to do is list the vertices counter-clockwise using the “positive y down” coordinates. The two effects then cancel out to produce a positive area.

Here is source code of the C++ Program to Implement Slicker Algorithm that avoids Triangulation to Find Area of a Polygon. The C++ program is successfully compiled and run on a Linux system. The program output is also shown below.

`#include <iostream>`

using namespace std;

const int MAXPOLY = 200;

double EPSILON = 0.000001;

`class Point`

`{`

private:

public:

double x, y;

};

`class Polygon`

`{`

private:

public:

Point p[MAXPOLY];

int n;

Polygon()

`{`

for (int i = 0; i < MAXPOLY; i++)

Point p[i];// = new Point();

`}`

};

double area(Polygon p)

`{`

double total = 0;

for (int i = 0; i < p.n; i++)

`{`

int j = (i + 1) % p.n;

total += (p.p[i].x * p.p[j].y) - (p.p[j].x * p.p[i].y);

`}`

return total / 2;

`}`

int main(int argc, char **argv)

`{`

`Polygon p;`

cout << "Enter the number of points in Polygon: ";

cin >> p.n;

cout << "Enter the coordinates of each point: <x> <y>";

for (int i = 0; i < p.n; i++)

`{`

cin >> p.p[i].x;

cin >> p.p[i].y;

`}`

double a = area(p);

if (a > 0)

cout << "The Area of Polygon with " << (p.n)

<< " points using Slicker Algorithm is : " << a;

`else`

cout << "The Area of Polygon with " << p.n

<< " points using Slicker Algorithm is : " << (a * -1);

`}`

Output:

$ g++ PloygonAreaSlickerAlgo.cpp $ a.out Enter the number of points in Polygon: 4 Enter the coordinates of each point: <x> <y> 1 1 1 6 6 6 6 1 The Area of Polygon with 4 points using Slicker Algorithm is : 25 Enter the number of points in Polygon: 5 Enter the coordinates of each point: <x> <y> 1 2 4 5 9 8 3 2 1 5 The Area of Polygon with 5points using Slicker Algorithm is : 6.0 ------------------ (program exited with code: 0) Press return to continue

**Sanfoundry Global Education & Learning Series – 1000 C++ Programs.**

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