kt: add «2516. Take K of Each Character From Left and Right»

URL:	https://leetcode.com/problems/take-k-of-each-character-from-left-and-right/
Signed-off-by: Matej Focko <me@mfocko.xyz>

kt/take-k-of-each-character-from-left-and-right.kt

@@ -0,0 +1,38 @@
+class Solution {
+    fun takeCharacters(
+        s: String,
+        k: Int,
+    ): Int {
+        val counters = IntArray(3)
+
+        // Get the frequencies
+        for (c in s) {
+            counters[c - 'a'] += 1
+        }
+
+        // Check for at least ‹k› characters
+        if (counters.any { it < k }) {
+            return -1
+        }
+
+        var l = 0
+        var maxWindow = 0
+
+        val window = IntArray(3)
+        for (r in s.indices) {
+            window[s[r] - 'a'] += 1
+
+            while (
+                l <= r &&
+                counters.zip(window).any { (c, w) -> c - w < k }
+            ) {
+                window[s[l] - 'a'] -= 1
+                l += 1
+            }
+
+            maxWindow = listOf(maxWindow, r - l + 1).max()
+        }
+
+        return s.length - maxWindow
+    }
+}