complete 6211.kt 27739.kt 30484.kt

storage/zeta/kt/completed/30484.kt

@@ -0,0 +1,39 @@
+const val DIVIDER = 1_000_000_007
+
+data class Counts(
+    var cntBiggers: Long,
+    var cntSmallers: Long
+)
+
+fun inversionCount(s: String, n: Long): Int {
+    val alphabetCounts = MutableList(26, { 0 });
+
+    val counts = Counts(0, 0)
+
+    s.forEach { ch ->
+        val index = ch.code - 'a'.code
+        val cntBiggers = alphabetCounts.slice(index + 1 until 26).sum()
+        val cntSmallers = alphabetCounts.slice(0 until index).sum()
+        alphabetCounts[index] += 1
+
+        counts.cntBiggers += cntBiggers
+        counts.cntSmallers += cntSmallers
+    }
+    val (n_mod: Long, np_mod: Long, nm_mod: Long) = if (n % 2 == 0L) {
+        Triple((n / 2) % DIVIDER, (n + 1) % DIVIDER, (n - 1) % DIVIDER)
+    } else {
+        Triple(n % DIVIDER, ((n + 1) / 2) % DIVIDER, ((n - 1) / 2) % DIVIDER)
+    }
+
+    return ((
+            (((((counts.cntBiggers % DIVIDER) * np_mod) % DIVIDER) * n_mod) % DIVIDER) + (((((counts.cntSmallers % DIVIDER) * n_mod) % DIVIDER) * nm_mod) % DIVIDER)
+            ) % DIVIDER
+            ).toInt()
+}
+
+fun main() = with(System.`in`.bufferedReader()) {
+    val s = readln().trim()
+    val n = readln().trim().toLong()
+
+    println(inversionCount(s, n))
+}