rs: add «1481. Least Number of Unique Integers after K Removals»

Signed-off-by: Matej Focko <mfocko@redhat.com>

rs/least-number-of-unique-integers-after-k-removals.rs

@@ -0,0 +1,49 @@
+use std::collections::HashMap;
+
+struct Solution {}
+impl Solution {
+    pub fn find_least_num_of_unique_ints(arr: Vec<i32>, mut k: i32) -> i32 {
+        // count
+        let mut freqs: HashMap<i32, i32> = HashMap::new();
+        for &x in &arr {
+            *freqs.entry(x).or_insert(0) += 1;
+        }
+
+        // make a list of frequencies
+        let mut counts: Vec<(i32, i32)> = freqs.into_iter().collect();
+        counts.sort_by_key(|&(_, count)| count);
+
+        // count the rest after removing k
+        let mut unique = counts.len() as i32;
+        for &(_, count) in &counts {
+            if count <= k {
+                unique -= 1;
+                k -= count;
+            }
+
+            if k == 0 || count > k {
+                break;
+            }
+        }
+
+        unique
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn example_1() {
+        assert_eq!(Solution::find_least_num_of_unique_ints(vec![5, 5, 4], 1), 1);
+    }
+
+    #[test]
+    fn example_2() {
+        assert_eq!(
+            Solution::find_least_num_of_unique_ints(vec![4, 3, 1, 1, 3, 3, 2], 3),
+            2
+        );
+    }
+}