Problem 1232

Author: YuqiZ2020

1232-Check-If-It-Is-a-Straight-Line.java

@@ -0,0 +1,32 @@
+/**
+ * Problem 1232: Check if it is a Straight Line
+ * Prompt: You are given an array coordinates, coordinates[i] = [x, y],
+ * where [x, y] represents the coordinate of a point. Check if these 
+ * points make a straight line in the XY plane.
+ * Date: 05/08/2020
+ */
+class Solution {
+    public boolean checkStraightLine(int[][] coordinates) {
+        int x_ini = coordinates[0][0];
+        int y_ini = coordinates[0][1];
+        //<v1, v2> is the vector created by the first two points
+        int v1 = coordinates[1][0] - x_ini;
+        int v2 = coordinates[1][1] - y_ini;
+        for (int i = 2; i < coordinates.length; ++i)
+        {
+            //<u1, u2> is the vector created by the 
+            //current point and the first point
+            int u1 = coordinates[i][0] - x_ini;
+            int u2 = coordinates[i][1] - y_ini;
+            if (v1 * u2 - u1 * v2 != 0)
+                return false;
+        }
+        return true;
+    }
+}
+
+/**
+ * Notes: record each points' relationship with the starting 
+ * point as a vector, and check if two vectors are parallel
+ * using the pseudo cross product. 
+ */