Code:
#include iostream
using namespace std;
// Define Infinite (Using INT_MAX caused overflow problems)
#define INF 10000
struct Point
{
int x;
int y;
};
// To find orientation of ordered triplet (p, q, r).
// The function returns following values
// 0 --> p, q and r are colinear
// 1 --> Clockwise
// 2 --> Counterclockwise
int orientation(Point p, Point q, Point r)
{
int val = (q.y - p.y) * (r.x - q.x) - (q.x - p.x) * (r.y - q.y);
if (val == 0)
return 0; // colinear
return (val > 0) ? 1 : 2; // clock or counterclock wise
}
// Prints convex hull of a set of n points.
void convexHull(Point points[], int n)
{
// There must be at least 3 points
if (n < 3)
return;
// Initialize Result
int next[n];
for (int i = 0; i < n; i++)
next[i] = -1;
// Find the leftmost point
int l = 0;
for (int i = 1; i < n; i++)
if (points[i].x < points[l].x)
l = i;
// Start from leftmost point, keep moving counterclockwise
// until reach the start point again
int p = l, q;
do
{
// Search for a point 'q' such that orientation(p, i, q) is
// counterclockwise for all points 'i'
q = (p + 1) % n;
for (int i = 0; i < n; i++)
if (orientation(points[p], points[i], points[q]) == 2)
q = i;
next[p] = q; // Add q to result as a next point of p
p = q; // Set p as q for next iteration
}
while (p != l);
// Print Result
for (int i = 0; i < n; i++)
{
if (next[i] != -1)
cout << "(" << points[i].x << ", " << points[i].y << ")\n";
}
}
// Driver program to test above functions
int main()
{
Point points[] = { { 0, 3 }, { 2, 2 }, { 1, 1 }, { 2, 1 }, { 3, 0 },
{ 0, 0 }, { 3, 3 } };
cout << "The points in the convex hull are: ";
int n = sizeof(points) / sizeof(points[0]);
convexHull(points, n);
return 0;
}
Output:
The points in the convex hull are: (0, 3)
(3, 0)
(0, 0)
(3, 3)
------------------
(program exited with code: 0)
Press return to continue
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