jarvis algorithm added

Author: Nadim-Mahmud

Source/Computetional Geometry/Jarvis Algorithm.cpp

@@ -0,0 +1,95 @@
+
+
+/// *** Jarvis Algorihtm [n*n]
+
+
+#define ll long long
+struct point{
+    ll x,y;
+}convex_points[MX],points[MX];;
+
+/// global scope decraltion of min-left point of collcetion
+point pivot;
+
+///Distance calculation mathod
+ll dist(point p1,point p2){
+    return ((p1.x-p2.x)*(p1.x-p2.x) + (p1.y-p2.y)*(p1.y-p2.y));
+}
+
+double distd(point p1,point p2){
+    return sqrt((p1.x-p2.x)*(p1.x-p2.x) + (p1.y-p2.y)*(p1.y-p2.y));
+}
+
+/**
+*   https://www.geeksforgeeks.org/orientation-3-ordered-points/
+*   calculating orientation based on slope (yi-yj)/(xi-xj)
+*   by compering slope of p-q and q-r;
+*   if p-q<q-r then counter-clockwise
+*   @return 0 if colinear
+*   @return 1 if clockwise (Right rotetion)
+*   @return 2 if counter-clockwise (left rotetion)
+*/
+int orientation(point p,point q,point r){
+    ll val = ((q.y-p.y)*(r.x-q.x) - (r.y-q.y)*(q.x-p.x));
+    if(val==0) return 0;
+    if(val>0) return 1;
+    return 2;
+}
+
+/**
+*   sorting by polor angle in counterclockwise order around point0.
+*   If polor angle of two points is same, then put the nearest point first.
+*/
+bool cmp(point p1,point p2){
+    ll o = orientation(pivot,p1,p2);
+    if(o==0){
+        return dist(pivot,p1) < dist(pivot,p2);
+    }
+    return (o==2);
+}
+
+/// returning previous value of top element
+inline point nextToTop(stack<point>&st){
+    point p,res;
+    p = st.top();
+    st.pop();
+    res = st.top();
+    st.push(p);
+    return res;
+}
+
+int total;
+
+/**
+*   This function will calculate convexHull points
+*   All arrays are in 0 based indexing
+*   @param n total numbers of points
+*/
+double convexHull(int n)
+{
+	vector<point> hull;
+	int l = 0;
+	for (int i = 1; i < n; i++)
+		if (points[i].x < points[l].x)
+			l = i;
+	int p = l, q;
+	do
+	{
+		hull.push_back(points[p]);
+		q = (p+1)%n;
+		for (int i = 0; i < n; i++)
+		{
+		if (orientation(points[p], points[i], points[q]) == 2)
+			q = i;
+		}
+
+		p = q;
+
+	} while (p != l);
+    double ans = distd(hull[0],hull[hull.size()-1]);
+	for (int i = 0; i<hull.size()-1; i++){
+        ans += distd(hull[i],hull[i+1]);
+        //cout<<hull[i].x<<" "<<hull[i].y<<endl;
+	}
+	return ans;
+}