Java实现的权重算法（按权重展现广告）

基本算法描述如下:

1、每个广告增加权重
2、将所有匹配广告的权重相加sum，
3、以相加结果为随机数的种子，生成1~sum之间的随机数rd
4、.接着遍历所有广告，访问顺序可以随意.将当前节点的权重值加上前面访问的各节点权重值得curWt,判断curWt >=  rd,如果条件成立则返回当前节点,如果不是则继续累加下一节点. 直到符合上面的条件,由于rd<=sum 因此一定存在curWt>=rd。
特别说明：

此算法和广告的顺序无关

import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;

public class Test {

  /**
   * @param args
   */
  @SuppressWarnings("unchecked")
  public static void main(String[] args) {

    List<Node> arrNodes = new ArrayList<Node>();
    Node n = new Node(10, "测试1");
    arrNodes.add(n);
    n = new Node(20, "测试2");
    arrNodes.add(n);
    n = new Node(30, "测试3");
    arrNodes.add(n);
    n = new Node(40, "测试4");
    arrNodes.add(n);

    //Collections.sort(arrNodes, new Node());
    Map<String, Integer> showMap = null;
    int sum = getSum(arrNodes);
    int random = 0;
    Node kw = null;
    for(int k = 0; k < 20; k++) {
      showMap = new LinkedHashMap<String, Integer>();
      for(int i = 0; i < 100; i++) {
        random = getRandom(sum);
        kw = getKW(arrNodes, random);
        if(showMap.containsKey(kw.kw)) {
          showMap.put(kw.kw, showMap.get(kw.kw) + 1);
        } else {
          showMap.put(kw.kw, 1);
        }
        //System.out.println(i + " " +random + " " + getKW(arrNodes, random));
      }
      System.out.print(k + " ");
      System.out.println(showMap);
    }
  }

  public static Node getKW(List<Node> nodes, int rd) {
    Node ret = null;
    int curWt = 0;
    for(Node n : nodes){
      curWt += n.weight;
      if(curWt >= rd) {
        ret = n;
        break;
      }
    }
    return ret;
  }
  public static int getSum(List<Node> nodes) {
    int sum = 0;
    for(Node n : nodes)
      sum += n.weight;
    return sum;
  }
  public static int getRandom(int seed) {
    return (int)Math.round(Math.random() * seed);
  }
}
class Node implements Comparator{
  int weight = 0;
  String kw = "";

  public Node() {}

  public Node(int wt, String kw) {
    this.weight = wt;
    this.kw = kw;
  }
  public String toString(){
    StringBuilder sbBuilder = new StringBuilder();
    sbBuilder.append(" weight=").append(weight);
    sbBuilder.append(" kw").append(kw);
    return sbBuilder.toString();
  }
  public int compare(Object o1, Object o2) {
    Node n1 = (Node)o1;
    Node n2 = (Node)o2;
    if(n1.weight > n2.weight)
      return 1;
    else
      return 0;
  }
}