From fafbeaf9e3c09ba7a5bea7e47d5736001f8a5aa1 Mon Sep 17 00:00:00 2001
From: HJ <thechairman@thechairman.info>
Date: Tue, 17 Jan 2023 12:46:04 -0500
Subject: adding old leetcode solutions

---
 leetcode/lc-1854-max-pop-year.rkt | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)
 create mode 100644 leetcode/lc-1854-max-pop-year.rkt

(limited to 'leetcode/lc-1854-max-pop-year.rkt')

diff --git a/leetcode/lc-1854-max-pop-year.rkt b/leetcode/lc-1854-max-pop-year.rkt
new file mode 100644
index 0000000..75104f1
--- /dev/null
+++ b/leetcode/lc-1854-max-pop-year.rkt
@@ -0,0 +1,17 @@
+#lang racket
+(define/contract (maximum-population logs)
+  (-> (listof (listof exact-integer?)) exact-integer?)
+  ; make a hash table of every year encountered between the birth and death years
+  (define population (make-hash))
+  ; for each person in the logs,
+  (for/list ([person (in-list logs)])
+    ; for every year from birth to the year before death,
+    (for/list ([year (in-range (first person) (second person))])
+      ; look up the year in the hash table and add 1 to its key,
+      ; or add the key and set its value to 1 if it doesn't exist yet
+      (hash-update! population year add1 1)))
+  ; convert the hash table to a list,
+  ; sort the list by year,
+  ; find the first element that maximizes the count,
+  ; and return the associated year
+  (car (argmax cdr (sort (hash->list population) < #:key car))))
\ No newline at end of file
-- 
cgit v1.2.3