From 647fbc935798d0810c52dada5c3c5f8286a49e1d Mon Sep 17 00:00:00 2001
From: EFanZh <efanzh@gmail.com>
Date: Sat, 11 Nov 2023 23:11:09 +0800
Subject: [PATCH] Add problem 1838: Frequency of the Most Frequent Element

---
 src/lib.rs                                    |  1 +
 .../mod.rs                                    | 23 +++++++++
 .../sliding_window.rs                         | 44 +++++++++++++++++
 .../sliding_window_2.rs                       | 47 +++++++++++++++++++
 4 files changed, 115 insertions(+)
 create mode 100644 src/problem_1838_frequency_of_the_most_frequent_element/mod.rs
 create mode 100644 src/problem_1838_frequency_of_the_most_frequent_element/sliding_window.rs
 create mode 100644 src/problem_1838_frequency_of_the_most_frequent_element/sliding_window_2.rs

diff --git a/src/lib.rs b/src/lib.rs
index d1ea9fec..046f9e7f 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -1440,6 +1440,7 @@ pub mod problem_1827_minimum_operations_to_make_the_array_increasing;
 pub mod problem_1832_check_if_the_sentence_is_pangram;
 pub mod problem_1833_maximum_ice_cream_bars;
 pub mod problem_1837_sum_of_digits_in_base_k;
+pub mod problem_1838_frequency_of_the_most_frequent_element;
 pub mod problem_1839_longest_substring_of_all_vowels_in_order;
 pub mod problem_1844_replace_all_digits_with_characters;
 pub mod problem_1845_seat_reservation_manager;
diff --git a/src/problem_1838_frequency_of_the_most_frequent_element/mod.rs b/src/problem_1838_frequency_of_the_most_frequent_element/mod.rs
new file mode 100644
index 00000000..b484d8e4
--- /dev/null
+++ b/src/problem_1838_frequency_of_the_most_frequent_element/mod.rs
@@ -0,0 +1,23 @@
+pub mod sliding_window;
+pub mod sliding_window_2;
+
+pub trait Solution {
+    fn max_frequency(nums: Vec<i32>, k: i32) -> i32;
+}
+
+#[cfg(test)]
+mod tests {
+    use super::Solution;
+
+    pub fn run<S: Solution>() {
+        let test_cases = [
+            ((&[1, 2, 4] as &[_], 5), 3),
+            ((&[1, 4, 8, 13], 5), 2),
+            ((&[3, 9, 6], 2), 1),
+        ];
+
+        for ((nums, k), expected) in test_cases {
+            assert_eq!(S::max_frequency(nums.to_vec(), k), expected);
+        }
+    }
+}
diff --git a/src/problem_1838_frequency_of_the_most_frequent_element/sliding_window.rs b/src/problem_1838_frequency_of_the_most_frequent_element/sliding_window.rs
new file mode 100644
index 00000000..cad251d4
--- /dev/null
+++ b/src/problem_1838_frequency_of_the_most_frequent_element/sliding_window.rs
@@ -0,0 +1,44 @@
+pub struct Solution;
+
+// ------------------------------------------------------ snip ------------------------------------------------------ //
+
+impl Solution {
+    pub fn max_frequency(nums: Vec<i32>, k: i32) -> i32 {
+        let mut nums = nums;
+
+        nums.sort_unstable();
+
+        let mut start = 0_usize;
+        let mut sum = 0;
+        let mut result = 0;
+
+        for (i, num) in (1..).zip(&nums) {
+            sum += num;
+
+            while num * (i - start) as i32 - sum > k {
+                sum -= nums[start];
+                start += 1;
+            }
+
+            result = result.max(i - start);
+        }
+
+        result as _
+    }
+}
+
+// ------------------------------------------------------ snip ------------------------------------------------------ //
+
+impl super::Solution for Solution {
+    fn max_frequency(nums: Vec<i32>, k: i32) -> i32 {
+        Self::max_frequency(nums, k)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    #[test]
+    fn test_solution() {
+        super::super::tests::run::<super::Solution>();
+    }
+}
diff --git a/src/problem_1838_frequency_of_the_most_frequent_element/sliding_window_2.rs b/src/problem_1838_frequency_of_the_most_frequent_element/sliding_window_2.rs
new file mode 100644
index 00000000..eb3196f9
--- /dev/null
+++ b/src/problem_1838_frequency_of_the_most_frequent_element/sliding_window_2.rs
@@ -0,0 +1,47 @@
+pub struct Solution;
+
+// ------------------------------------------------------ snip ------------------------------------------------------ //
+
+impl Solution {
+    pub fn max_frequency(nums: Vec<i32>, k: i32) -> i32 {
+        let mut nums = nums;
+
+        nums.sort_unstable();
+
+        let mut start = 0_usize;
+        let mut required = 0;
+        let mut result = 0;
+        let mut prev = 0;
+
+        for (i, &num) in nums.iter().enumerate() {
+            required += (num - prev) * (i - start) as i32;
+
+            while required > k {
+                required -= num - nums[start];
+                start += 1;
+            }
+
+            result = result.max(i + 1 - start);
+
+            prev = num;
+        }
+
+        result as _
+    }
+}
+
+// ------------------------------------------------------ snip ------------------------------------------------------ //
+
+impl super::Solution for Solution {
+    fn max_frequency(nums: Vec<i32>, k: i32) -> i32 {
+        Self::max_frequency(nums, k)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    #[test]
+    fn test_solution() {
+        super::super::tests::run::<super::Solution>();
+    }
+}