Java实现按权重随机数
一、问题定义：
问下有一个数组，这些数组中的值都有自己的权重，怎样设计才能高效的优先取出权重高的数？？
例如：
79331356@qq.com
2014-2-16 21:12
输出结果：{2.0=184128, 11.0=348551, 79.0=1308100, 8.0=159221}
*/
public class WeightRandomTest {
private static double[] weightArrays = {8.0,2.0,11.0,79.0}; // 数组下标是要返回的值，数组值为数组下标的权重
public static void main(String[] args) {
WeightRandom weightRandom = new WeightRandom();
Map<Double, Integer> stat = new HashMap<Double, Integer>();
for (int i = 0; i < 2000000; i++) {
int weightValue = weightRandom.getWeightRandom(weightArrays);
if (weightValue < 0) {
continue;
}
System.out.println("按权重返回的随机数：" + weightValue);
if (stat.get(weightArrays[weightValue]) == null) {
stat.put(weightArrays[weightValue], 1);
} else {
stat.put(weightArrays[weightValue], stat.get(weightArrays[weightValue])+1);
}
}
System.out.println(stat);
}
}
class WeightRandom {
java.util.Random r = new java.util.Random();
private double weightArraySum(double [] weightArrays) {
double weightSum = 0;
for (double weightValue : weightArrays) {
weightSum += weightValue;
}
return weightSum;
}
public int getWeightRandom(double [] weightArrays) {
double weightSum = weightArraySum(weightArrays);
double stepWeightSum = 0;
for (int i = 0; i < weightArrays.length; i++) {
stepWeightSum += weightArrays[i];
if (Math.random() <= stepWeightSum/weightSum) {
//System.out.println(i);
return i;
}
}
System.out.println("出错误了");
return -1;
}
}
四、归纳总结：
俄罗斯轮盘赌就是积累概率来实现
按权重负载调度等
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