红包雨-红包发放

activity-admin/src/main/java/com/polysoft/activity/constant/RedPacketUtil.java

+package com.polysoft.activity.constant;
+
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * @author lvyp
+ * @date 2021/1/29
+ * 红包算法分析
+ * 1.设置金额的上下限 2.判断金额是否合法 3.随机产生红包
+ */
+public class RedPacketUtil {
+    //1.设置金额的上下限   最少0.01，最多200
+    private  double MINMONEY ;
+    private  double MAXMONEY ;
+    private  double TIMES ;
+    /**
+     * 4.实现红包分配，为了避免一个红包占用大量的金额，设定非最后一个红包的 最大金额，可以设置平均值的N陪，
+     *
+     * */
+    public List<Double> splitRedPackets(double money, int count) {
+        if (!isRight(money, count)) {
+            return null;
+        }
+        List<Double> list = new ArrayList<Double>();
+        double max = (double) (money * TIMES / count);
+
+        max = max > MAXMONEY ? MAXMONEY : max;
+        for (int i = 0; i < count; i++) {
+            double one = randomRedPacket(money, MINMONEY, max, count - i);
+            list.add(one);
+            money -= one;
+        }
+        return list;
+    }
+    /**
+     * 3.随机产生红包
+     *
+     * */
+    private double randomRedPacket(double money, double mins, double maxs, int count) {
+        if (count == 1) {
+            return (double) (Math.round(money * 100)) / 100;
+        }
+        if (mins == maxs) {
+            return mins;
+        }
+        double max = maxs > money ? money : maxs;
+        double one = ((double) Math.random() * (max - mins) + mins);
+        one = (double) (Math.round(one * 100)) / 100;
+        double moneyOther = money - one;
+        if (isRight(moneyOther, count - 1)) {
+            return one;
+        } else {
+
+            double avg = moneyOther / (count - 1);
+            if (avg < MINMONEY) {
+                return randomRedPacket(money, mins, one, count);
+            } else if (avg > MAXMONEY) {
+                return randomRedPacket(money, one, maxs, count);
+            }
+        }
+        return one;
+    }
+
+    public RedPacketUtil(double MINMONEY, double MAXMONEY, double TIMES) {
+        this.MINMONEY = MINMONEY;
+        this.MAXMONEY = MAXMONEY;
+        this.TIMES = TIMES;
+    }
+
+    //2.判断金额是否合法  如果超过了最大值与最小值，错误
+    private boolean isRight(double money, int count) {
+        double avg = money / count;
+        if (avg < MINMONEY) {
+            return false;
+        } else if (avg > MAXMONEY) {
+            return false;
+        }
+        return true;
+    }
+
+    public static void main(String[] args) {
+
+        RedPacketUtil util = new RedPacketUtil(5,100,2);
+        List<Double> doubles = util.splitRedPackets(1250, 100);
+        doubles.forEach(item -> System.out.println(item));
+    }
+}

activity-admin/src/main/java/com/polysoft/activity/constant/Test.java

-package com.polysoft.activity.constant;
-
-import java.text.DecimalFormat;
-import java.text.NumberFormat;
-import java.util.ArrayList;
-import java.util.Collections;
-import java.util.List;
-import java.util.Random;
-import java.util.Scanner;
-
-/**
- * @author lvyp
- * @date 2021/1/29
- */
-public class Test {
-    public static void main(String[] args) {
-        //红包数
-        int number = 10;
-        //红包总额
-        float total = 100;
-        float money;
-        //最小红包
-        double min = 1;
-        double max;
-        int i = 1;
-        List math = new ArrayList();
-        DecimalFormat df = new DecimalFormat("###.##");
-        while (i < number) {
-            //保证即使一个红包是最大的了,后面剩下的红包,每个红包也不会小于最小值
-            max = total - min * (number - i);
-            int k = (int)(number - i) / 2;
-            //保证最后两个人拿的红包不超出剩余红包
-            if (number - i <= 2) {
-                k = number - i;
-            }
-            //最大的红包限定的平均线上下
-            max = max / k;
-            //保证每个红包大于最小值,又不会大于最大值
-            money = (int) (min * 100 + Math.random() * (max * 100 - min * 100 + 1));
-            money = (float)money / 100;
-            //保留两位小数
-            money = Float.parseFloat(df.format(money));
-            total=(int)(total*100 - money*100);
-            total = total/100;
-            math.add(money);
-            System.out.println("第" + i + "个人拿到" + money + "剩下" + total);
-            i++;
-            //最后一个人拿走剩下的红包
-            if (i == number) {
-                math.add(total);
-                System.out.println("第" + i + "个人拿到" + total + "剩下0");
-            }
-        }
-//取数组中最大的一个值的索引
-        System.out.println("本轮发红包中第" + (math.indexOf(Collections.max(math)) + 1) + "个人手气最佳");
-    }
-}