feat(8-kyu): kata/collinearity

docs/README.md

@@ -25,7 +25,7 @@ slug.
 
 | [1 kyu](/kata/1-kyu/index.md) | [2 kyu](/kata/2-kyu/index.md) | [3 kyu](/kata/3-kyu/index.md) | [4 kyu](/kata/4-kyu/index.md) | [5 kyu](/kata/5-kyu/index.md) | [6 kyu](/kata/6-kyu/index.md) | [7 kyu](/kata/7-kyu/index.md) | [8 kyu](/kata/8-kyu/index.md) | [beta](/kata/beta/index.md) | [retired](/kata/retired/index.md) |
 |:-----------------------------:|:-----------------------------:|:-----------------------------:|:-----------------------------:|:-----------------------------:|:-----------------------------:|:-----------------------------:|:-----------------------------:|:---------------------------:|:---------------------------------:|
-| 0 | 1 | 2 | 26 | 44 | 421 | 562 | 208 | 55 | 79 |
+| 0 | 1 | 2 | 26 | 44 | 421 | 562 | 209 | 55 | 79 |
 
 **Note:** The source code is written in Java 17 and may use language features that are incompatible
 with Java 8, 11.

kata/8-kyu/collinearity/README.md

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+# [Collinearity](https://www.codewars.com/kata/collinearity "https://www.codewars.com/kata/65ba420888906c1f86e1e680")
+
+## Theoretical Material
+
+You are given two vectors starting from the origin (x=0, y=0) with coordinates (x1,y1) and (x2,y2). Your task is to find
+out if these vectors are collinear. Collinear vectors are vectors that lie on the same straight line. They can be
+directed in the same or opposite directions. One vector can be obtained from another by multiplying it by a certain
+number. In terms of coordinates, vectors (x1, y1) and (x2, y2) are collinear if (x1, y1) = (k\*x2, k\*y2) , where k is
+any number acting as a coefficient.
+
+![](https://d138zd1ktt9iqe.cloudfront.net/media/seo_landing_files/collinear-vectors-1627481628.png)
+
+For more information, check out this [article on collinearity](https://www.cuemath.com/geometry/collinear-vectors/).
+
+## Problem Description
+
+Write the function `collinearity(x1, y1, x2, y2)`, which returns a Boolean type depending on whether the vectors are
+collinear or not.
+
+```
+all coordinates are integers
+-1000 <= any coordinate <= 1000
+```
+
+## Notes
+
+- All vectors start from the origin (x=0, y=0).
+- Be careful when handling cases where x1, x2, y1, or y2 are zero to avoid division by zero errors.
+- A vector with coordinates (0, 0) is collinear to all vectors.
+
+## Examples
+
+```
+(1,1,1,1) ➞ true
+(1,2,2,4) ➞ true
+(1,1,6,1) ➞ false
+(1,2,-1,-2) ➞ true
+(1,2,1,-2) ➞ false
+(4,0,11,0) ➞ true
+(0,1,6,0) ➞ false
+(4,4,0,4) ➞ false
+(0,0,0,0) ➞ true
+(0,0,1,0) ➞ true
+(5,7,0,0) ➞ true
+```

kata/8-kyu/collinearity/main/Kata.java

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+interface Kata {
+  static boolean collinearity(int x1, int y1, int x2, int y2) {
+    return x1 * y2 == y1 * x2;
+  }
+}

kata/8-kyu/collinearity/test/SolutionTest.java

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+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.CsvSource;
+
+class SolutionTest {
+  @ParameterizedTest
+  @CsvSource(textBlock = """
+      0, 0, 0, 0
+      0, 0, 1, 0
+      1, 1, 1, 1
+      1, 2, 2, 4
+      1, 1, -1, -1
+      1, -2, -2, 4
+      4, 0, 11, 0
+      5, 7, 0, 0
+      """)
+  void collinear(int x1, int y1, int x2, int y2) {
+    assertTrue(Kata.collinearity(x1, y1, x2, y2));
+  }
+
+  @ParameterizedTest
+  @CsvSource(textBlock = """
+      0, 1, 6, 0
+      1, 1, 6, 1
+      1, 2, 1, -2
+      4, 4, 0, 4
+      -9, 171, -574, -214
+      """)
+  void nonCollinear(int x1, int y1, int x2, int y2) {
+    assertFalse(Kata.collinearity(x1, y1, x2, y2));
+  }
+}