kt: add «3160. Find the Number of Distinct Colors Among the Balls»

URL:	https://leetcode.com/problems/find-the-number-of-distinct-colors-among-the-balls/
Signed-off-by: Matej Focko <me@mfocko.xyz>

kt/find-the-number-of-distinct-colors-among-the-balls.kt

@@ -0,0 +1,28 @@
+class Solution {
+    fun queryResults(
+        limit: Int,
+        queries: Array<IntArray>,
+    ): IntArray {
+        val n = queries.size
+        val freqs = mutableMapOf<Int, Int>()
+        val balls = mutableMapOf<Int, Int>()
+
+        return queries.map { q ->
+            val (ball, color) = q[0] to q[1]
+
+            if (balls.containsKey(ball)) {
+                val currentColor = balls[ball]!!
+                freqs.put(currentColor, freqs.get(currentColor)!! - 1)
+
+                if (freqs[currentColor] == 0) {
+                    freqs.remove(currentColor)
+                }
+            }
+
+            balls[ball] = color
+            freqs[color] = 1 + (freqs.get(color) ?: 0)
+
+            freqs.size
+        }.toIntArray()
+    }
+}