adding old leetcode solutions

1 files changed, 21 insertions, 0 deletions

diff --git a/leetcode/lc-1037-boomerang.rkt b/leetcode/lc-1037-boomerang.rkt
new file mode 100644
index 0000000..fd95695
--- /dev/null
+++ b/leetcode/lc-1037-boomerang.rkt
@@ -0,0 +1,21 @@
+#lang racket
+(define/contract (is-boomerang points)
+  (-> (listof (listof exact-integer?)) boolean?)
+  (match points
+    [(list-no-order a b c) #:when (equal? a b) #false]    ; Are any two points the same?
+    [(list (list x _) (list x _) (list x _)) #false]      ; Are they on a horizontal line?
+    [(list (list _ y) (list _ y) (list _ y)) #false]      ; Are they on a vertical line?
+    [(list-no-order (list x1 _) (list x2 _) (list x3 _))  ; Are two points on a horizontal line,
+     #:when (and (= x1 x2)                                ; but the third point isn't?
+                 (not (= x1 x3))) #true]
+    [(list-no-order (list _ y1) (list _ y2) (list _ y3))  ; Are two points on a vertical line,
+     #:when (and (= y1 y2)                                ; but the third point isn't?
+                 (not (= y1 y3))) #true]
+    [(list (list x1 y1) (list x2 y2) (list x3 y3))        ; If none of the special cases apply,
+     (let ([m (/ (- y2 y1) (- x2 x1))])                   ; calculate the slope between two points
+       (not (= y3 (+ y1 (* m (- x3 x1))))))]))            ; and see if the line passes through the third
+
+(is-boomerang '((1 1) (2 3) (3 2)))
+(is-boomerang '((1 1) (2 2) (3 3)))
+(is-boomerang '((0 0) (0 2) (2 1)))
+(is-boomerang '((0 0) (1 1) (1 1)))
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