JAVA抽奖的算概率法
php:
data.php处理前端发送的ajax请求，我们才用概率算法，根据设置好的中奖概率，将中奖结果以json的格式输出。关于概率计算的例子可以参照：PHP+jQuery实现翻板抽奖
$prize_arr = array(
"0" => array("id"=>1,"prize"=>"平板电脑","v"=>3),
"1" => array("id"=>2,"prize"=>"数码相机","v"=>5),
"2" => array("id"=>3,"prize"=>"音箱设备","v"=>10),
"3" => array("id"=>4,"prize"=>"4G优盘","v"=>12),
"4" => array("id"=>5,"prize"=>"Q币10元","v"=>20),
"5" => array("id"=>6,"prize"=>"下次没准就能中哦","v"=>50),
);
foreach ($prize_arr as $key => $val) {
$arr[$val["id"]] = $val["v"];
}
$rid = getRand($arr); //根据概率获取奖项id
$res["msg"] = ($rid==6)?0:1; //如果为0则没中
$res["prize"] = $prize_arr[$rid-1]["prize"]; //中奖项
echo json_encode($res);
//计算概率
function getRand($proArr) {
$result = "";
//概率数组的总概率精度
$proSum = array_sum($proArr);
//概率数组循环
foreach ($proArr as $key => $proCur) {
$randNum = mt_rand(1, $proSum);
if ($randNum <= $proCur) {
$result = $key;
break;
} else {
$proSum -= $proCur;
}
}
unset ($proArr);
return $result;
}
优先级规则使高等奖尽量在后期抽出
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import java.util.LinkedList;
import java.util.List;
public class GetGift {
// 奖品仓库
private List<Gift> gifts = new LinkedList<Gift>();
public GetGift() {
// 生成一堆奖品放进奖品仓库
// 一等奖一个优先级1，二等奖两个优先级2。。。20等奖20个优先级20
for (int i = 1; i <= 20; i++) {
GiftType gt = new GiftType(i + "等奖", i, i);
for (int j = 1; j <= i; j++) {
gifts.add(new Gift(i + "等奖——第" + j + "号", gt));
}
}
}
// 抽奖
public synchronized Gift getGift() {
int randomNumber = (int) (Math.random() * total());
int priority = 0;
for (Gift g : gifts) {
priority += g.getType().getPriority();
if (priority >= randomNumber) {
// 从奖品库移出奖品
gifts.remove(g);
return g;
}
}
// 抽奖次数多于奖品时，没有奖品
return null;
}
/**
* @param args
*/
public static void
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