From 5494c1d4881bb8396d2f72b6c920a9d52a2f3739 Mon Sep 17 00:00:00 2001
From: xiongraorao <xiongraorao@gmail.com>
Date: Fri, 7 Sep 2018 00:14:16 +0800
Subject: [PATCH] =?UTF-8?q?=E7=BD=91=E6=98=93=E5=90=88=E5=94=B1=E5=9B=A2?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 .../java/com/raorao/nowcoder/HeChangTuan.java | 63 +++++++++++++++++++
 1 file changed, 63 insertions(+)
 create mode 100644 code/src/main/java/com/raorao/nowcoder/HeChangTuan.java

diff --git a/code/src/main/java/com/raorao/nowcoder/HeChangTuan.java b/code/src/main/java/com/raorao/nowcoder/HeChangTuan.java
new file mode 100644
index 00000000..4a9cce7a
--- /dev/null
+++ b/code/src/main/java/com/raorao/nowcoder/HeChangTuan.java
@@ -0,0 +1,63 @@
+package com.raorao.nowcoder;
+
+import java.util.Scanner;
+
+/**
+ * 牛客网：合唱团问题
+ *
+ * https://www.nowcoder.com/questionTerminal/661c49118ca241909add3a11c96408c8?orderByHotValue=1&mutiTagIds=593&page=1&onlyReference=false.
+ *
+ * @author Xiong Raorao
+ * @since 2018-09-06-23:21
+ */
+public class HeChangTuan {
+
+  public static void main(String[] args) {
+    Scanner scanner = new Scanner(System.in);
+    int n = scanner.nextInt();
+    int[] a = new int[n + 1];
+    for (int i = 1; i < n + 1; i++) {
+      a[i] = scanner.nextInt();
+    }
+    int kk = scanner.nextInt();
+    int dd = scanner.nextInt();
+
+    // 规划数组
+    long[][] f = new long[n + 1][kk + 1];
+    long[][] g = new long[n + 1][kk + 1];
+
+    //初始化k = 1
+    for (int one = 1; one <= n; one++) {
+      f[one][1] = a[one];
+      g[one][1] = a[one];
+    }
+
+    // 自底向上递推
+    for (int k = 2; k <= kk; k++) {
+      for (int one = k; one <= n; one++) {
+        // 求解当one和k定下来的时候，最大的分割点
+        long tempMax = Long.MIN_VALUE;
+        long tempMin = Long.MAX_VALUE;
+        for (int left = Math.max(k - 1, one - dd); left <= one - 1; left++) {
+          if (tempMax < Math.max(f[left][k - 1] * a[one], g[left][k - 1] * a[one])) {
+            tempMax = Math.max(f[left][k - 1] * a[one], g[left][k - 1] * a[one]);
+          }
+          if (tempMin > Math.min(f[left][k - 1] * a[one], g[left][k - 1] * a[one])) {
+            tempMin = Math.min(f[left][k - 1] * a[one], g[left][k - 1] * a[one]);
+          }
+          f[one][k] = tempMax;
+          g[one][k] = tempMin;
+        }
+      }
+    }
+    //n选k最大的需要从最后一个最大的位置选
+    long result = Long.MIN_VALUE;
+    for (int one = kk; one <= n; one++) {
+      if (result < f[one][kk]) {
+        result = f[one][kk];
+      }
+    }
+    System.out.println(result);
+
+  }
+}