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| 1 | +/// A C++ program to find convex hull of a set of points. |
| 2 | +#include <bits/stdc++.h> |
| 3 | +using namespace std; |
| 4 | + |
| 5 | +class Point |
| 6 | +{ |
| 7 | + public: |
| 8 | + int x, y; |
| 9 | +}; |
| 10 | + |
| 11 | +int find_orientation(Point p, Point q, Point r) |
| 12 | +{ |
| 13 | + int val = (q.y - p.y) * (r.x - q.x) - |
| 14 | + (q.x - p.x) * (r.y - q.y); |
| 15 | + |
| 16 | + if (val == 0) return 0; |
| 17 | + return (val > 0)? 1: 2; |
| 18 | +} |
| 19 | + |
| 20 | +void convexHull(Point points[], int n) |
| 21 | +{ |
| 22 | + if (n < 3) return; |
| 23 | + vector<Point> hull; |
| 24 | + int l = 0; |
| 25 | + for (int i = 1; i < n; i++) |
| 26 | + if (points[i].x < points[l].x) |
| 27 | + l = i; |
| 28 | + int p = l, q; |
| 29 | + do |
| 30 | + { |
| 31 | + hull.push_back(points[p]); |
| 32 | + q = (p+1)%n; |
| 33 | + for (int i = 0; i < n; i++) |
| 34 | + { |
| 35 | + if (find_orientation(points[p], points[i], points[q]) == 2) |
| 36 | + q = i; |
| 37 | + } |
| 38 | + p = q; |
| 39 | + |
| 40 | + } while (p != l); |
| 41 | + for (int i = 0; i < hull.size(); i++) |
| 42 | + cout << "(" << hull[i].x << ", " |
| 43 | + << hull[i].y << ")\n"; |
| 44 | +} |
| 45 | + |
| 46 | +int main() |
| 47 | +{ |
| 48 | + Point points[] = {{0, 3}, {2, 2}, {1, 1}, {2, 1}, |
| 49 | + {3, 0}, {0, 0}, {3, 3}}; |
| 50 | + int n = sizeof(points)/sizeof(points[0]); |
| 51 | + convexHull(points, n); |
| 52 | + return 0; |
| 53 | +} |
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