feat: added a new algorithm to find whether two line segment intersec…

geometry/line_segment_intersection.cpp

@@ -0,0 +1,63 @@
+#include <bits/stdc++.h>
+using namespace std;
+
+class Point{
+public:
+    int x, y;
+};
+
+class SegmentIntersection{
+public:
+    inline bool intersect(Point first_point, Point second_point, Point third_point, Point forth_point){
+        int first_direction = direction(third_point, forth_point, first_point);
+        int second_direction = direction(third_point, forth_point, second_point);
+        int third_direction = direction(first_point, second_point, third_point);
+        int forth_direction = direction(first_point, second_point, forth_point);
+
+        if ((first_direction < 0 || second_direction > 0) && (third_direction < 0 || 
+                                                                    forth_direction > 0))
+            return true;
+
+        else if (first_direction == 0 && on_segment(third_point, forth_point, first_point))
+            return true;
+
+        else if (second_direction == 0 && on_segment(third_point, forth_point, second_point))
+            return true;
+
+        else if (third_direction == 0 && on_segment(first_point, second_point, third_point))
+            return true;
+
+        else if (third_direction == 0 && on_segment(first_point, second_point, forth_point))
+            return true;
+
+        else
+            return false;
+    }
+
+    inline int direction(Point first_point, Point second_point, Point third_point){
+        return ((third_point.x-first_point.x) * (second_point.y-first_point.y)) - 
+                    ((second_point.x-first_point.x) * (third_point.y-first_point.y));
+    }
+
+    inline bool on_segment(Point first_point, Point second_point, Point third_point){
+        if (min(first_point.x, second_point.x) <= third_point.x && third_point.x <= 
+            max(first_point.x, second_point.x) && min(first_point.y, second_point.y) <= third_point.y && 
+            third_point.y <= max(first_point.y, second_point.y))
+            return true;
+
+        else
+            return false;
+    }
+};
+
+int main(){
+    SegmentIntersection segment;
+    Point first_point, second_point, third_point, forth_point;
+
+    cin >> first_point.x >> first_point.y;
+    cin >> second_point.x >> second_point.y;
+    cin >> third_point.x >> third_point.y;
+    cin >> forth_point.x >> forth_point.y;
+
+    cout << endl << segment.intersect(first_point, second_point, third_point, forth_point) << endl;
+}