complete 34219.kt 34239.kt

storage/zeta/kt/completed/34239.kt

@@ -0,0 +1,67 @@
+import kotlin.math.max
+import kotlin.math.min
+import kotlin.random.Random
+
+data class Element(
+    var consMin: Long, var consMax: Long, var onlyOne: Long, var noChoose: Long
+) {
+    fun max(): Long = max(max(consMax, consMin), max(onlyOne, noChoose))
+}
+
+fun maximaAlternatingSum(arr: List<Long>): Long {
+    if (arr.size == 1) {
+        return arr.first()
+    }
+    val dp = mutableListOf<Element>()
+    dp.add(Element(arr.last(), arr.last(), arr.last(), Long.MIN_VALUE))
+
+    for (x in arr.slice(0 until arr.size - 1).reversed()) {
+        val last = dp.last()
+
+        val e: Element = Element(0, 0, 0, 0)
+
+        e.consMax = max(x - last.consMin, x - last.onlyOne)
+        e.consMin = min(x - last.consMax, x - last.onlyOne)
+        e.onlyOne = x
+        e.noChoose = last.max()
+
+        //println(e)
+        dp.add(e)
+    }
+
+    return dp.last().max()
+}
+
+fun testAltSum(arr: List<Long>): Long {
+    var m = Long.MIN_VALUE
+    val cum1 = mutableListOf<Long>()
+    val cum2 = mutableListOf<Long>()
+    cum1.add(0)
+    cum2.add(0)
+
+    var sign = -1
+
+    for (item in arr) {
+        sign *= -1
+        cum1.add(cum1.last() + sign * item)
+        cum2.add(cum2.last() - sign * item)
+    }
+
+    for (l in 0 until arr.size) {
+        for (r in l + 1..arr.size) {
+            val s = if (l % 2 == 0) {
+                cum1[r] - cum1[l]
+            } else {
+                cum2[r] - cum2[l]
+            }
+            m = max(s, m)
+        }
+    }
+    return m
+}
+
+fun main() = with(System.`in`.bufferedReader()) {
+    this.readLine()
+    val arr = this.readLine().split(" ").map { it.toLong() }
+    println(maximaAlternatingSum(arr))
+}