随机物品权重算法设计

1、前言
在游戏开发中很多功能按权重随机给东西，比如：掉落、奖励、抽奖等等.....

2、功能

*）支持多个权重进行随机

*）能屏蔽指定权重，防止再次随机到

3、实现

public int weightRandom(BitSet exclude, int... weights) {
        if (weights == null) {
            //安全性验证
        }
        int length = weights.length;
        if (length == 0) {
            return -1;
        }

        if (len == 1) {
            int w = weights[0];
            if (w < 0) {
                //安全性验证
            } else if (w == 0) {
                return -1;
            } else {
                return 0;
            }
        }

        int total = 0;
        for (int i = 0; i < len; i++) {
            if (exclude != null && exclude.get(i)) {
                continue;
            }
            int w = weights[i];
            total += w;
        }
        if (total <= 0) {
            return -1;
        }
        int randomNum = random(1, total), hitIndex = -1, partNum = 0;
        for (int i = 0; i < len; i++) {
            if (exclude != null && exclude.get(i)) {
                continue;
            }
            int w = weights[i];
            partNum += w;
            if (partNum >= randomNum) {
                hitIndex = i;
                break;
            }
        }
        return hitIndex;
}