Data Structure
Networking
RDBMS
Operating System
Java
MS Excel
iOS
HTML
CSS
Android
Python
C Programming
C++
C#
MongoDB
MySQL
Javascript
PHP
Physics
Chemistry
Biology
Mathematics
English
Economics
Psychology
Social Studies
Fashion Studies
Legal Studies
- Selected Reading
- UPSC IAS Exams Notes
- Developer's Best Practices
- Questions and Answers
- Effective Resume Writing
- HR Interview Questions
- Computer Glossary
- Who is Who
C++ Program to implement Gift Wrapping Algorithm in Two Dimensions
We shall develop a C++ program to implement Gift Wrapping Algorithm in two dimensions. The Gift Wrapping Algorithm is an algorithm for computing the convex hull of a given set of points.
Algorithm
Begin function convexHull() to find convex hull of a set of n points: There must be at least three points. Initialize the result. Find the leftmost point. Starting from leftmost point, keep moving counterclockwise until reach the start point again. Print the result. End
Example Code
#include <iostream>
using namespace std;
#define INF 10000
struct P {
int x;
int y;
};
int orient(P a, P b, P c) {
int v = (b.y - a.y) * (c.x - b.x) - (b.x - a.x) * (c.y - b.y);
if (v == 0)
return 0; // colinear
return (v >0) ? 1 : 2; // clock or counterclock wise
}
void convexHull(P points[], int m) {
if (m < 3)//at least three points required
return;
int n[m];
for (int i = 0; i < m; i++)
n[i] = -1;
int l = 0;//initialize result.
for (int i = 1; i < m; i++)
if (points[i].x < points[l].x)
l = i; //find left most point
int p = l, q;
do {
q = (p + 1) % m;
for (int i = 0; i < m; i++)
if (orient(points[p], points[i], points[q]) == 2)
q = i;
n[p] = q;
p = q;
} while (p != l);
for (int i = 0; i < m; i++) {
if (n[i] != -1)
cout << "(" << points[i].x << ", " << points[i].y << ")\n";
}
}
int main() {
P points[] = {{0, 4}, {2, 1}, {2, 3}, {4, 1}, {3, 0}, {1, 1}, {7, 6}};
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, 4) (4, 1) (3, 0) (1, 1) (7, 6)
Updated on: 30-Jul-2019
353 Views
Advertisements