rs: add «992. Subarrays with K Different Integers»

Signed-off-by: Matej Focko <me@mfocko.xyz>

rs/subarrays-with-k-different-integers.rs

@@ -0,0 +1,39 @@
+impl Solution {
+    pub fn subarrays_with_k_distinct(nums: Vec<i32>, mut k: i32) -> i32 {
+        let mut freqs = vec![0; nums.len() + 1];
+
+        let mut count = 0;
+        let mut current_count = 0;
+
+        let mut i = 0;
+        let mut j = 0;
+        while j < nums.len() {
+            freqs[nums[j] as usize] += 1;
+            if freqs[nums[j] as usize] == 1 {
+                k -= 1;
+            }
+            j += 1;
+
+            if k < 0 {
+                freqs[nums[i] as usize] -= 1;
+                k += 1;
+                current_count = 0;
+
+                i += 1;
+            }
+
+            if k == 0 {
+                while freqs[nums[i] as usize] > 1 {
+                    freqs[nums[left] as usize] -= 1;
+                    current_count += 1;
+
+                    i += 1;
+                }
+
+                count += current_count + 1;
+            }
+        }
+
+        count
+    }
+}