Add a new soluton to problem 2183: Count Array Pairs Divisible by K

src/problem_2183_count_array_pairs_divisible_by_k/gcd_and_hash_map_2.rs

@@ -0,0 +1,67 @@
+pub struct Solution;
+
+// ------------------------------------------------------ snip ------------------------------------------------------ //
+
+use std::cmp::Ordering;
+use std::collections::hash_map::Entry;
+use std::collections::HashMap;
+use std::num::NonZeroU32;
+
+impl Solution {
+    fn gcd(mut x: u32, mut y: NonZeroU32) -> NonZeroU32 {
+        while let Some(z) = NonZeroU32::new(x % y) {
+            x = y.get();
+            y = z;
+        }
+
+        y
+    }
+
+    pub fn count_pairs(nums: Vec<i32>, k: i32) -> i64 {
+        let k = NonZeroU32::new(k as _).unwrap();
+        let mut counts = HashMap::<_, u64>::new();
+
+        for num in nums {
+            match counts.entry(Self::gcd(num as _, k)) {
+                Entry::Occupied(entry) => *entry.into_mut() += 1,
+                Entry::Vacant(entry) => {
+                    entry.insert(1);
+                }
+            }
+        }
+
+        let mut result = 0;
+
+        for (&gcd_1, &count_1) in &counts {
+            let required = NonZeroU32::new(k.get() / gcd_1).unwrap();
+
+            for (&gcd_2, &count_2) in &counts {
+                if gcd_2.get() % required == 0 {
+                    result += match gcd_1.cmp(&gcd_2) {
+                        Ordering::Less => count_1 * count_2,
+                        Ordering::Equal => count_1 * (count_1 - 1) / 2,
+                        Ordering::Greater => continue,
+                    };
+                }
+            }
+        }
+
+        result as _
+    }
+}
+
+// ------------------------------------------------------ snip ------------------------------------------------------ //
+
+impl super::Solution for Solution {
+    fn count_pairs(nums: Vec<i32>, k: i32) -> i64 {
+        Self::count_pairs(nums, k)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    #[test]
+    fn test_solution() {
+        super::super::tests::run::<super::Solution>();
+    }
+}

src/problem_2183_count_array_pairs_divisible_by_k/mod.rs

@@ -1,4 +1,5 @@
 pub mod gcd_and_hash_map;
+pub mod gcd_and_hash_map_2;
 
 pub trait Solution {
     fn count_pairs(nums: Vec<i32>, k: i32) -> i64;