不会就坚持66天吧 权重生成随机数

 

class Solution {
    int[] pre;
    int total;
    
    public Solution(int[] w) {
        pre = new int[w.length];
        pre[0] = w[0];
        for (int i = 1; i < w.length; ++i) {
            pre[i] = pre[i - 1] + w[i];
        }
        total = Arrays.stream(w).sum();
    }
    
    public int pickIndex() {
        int x = (int) (Math.random() * total) + 1;
        return binarySearch(x);
    }

    private int binarySearch(int x) {
        int low = 0, high = pre.length - 1;
        while (low < high) {
            int mid = (high - low) / 2 + low;
            if (pre[mid] < x) {
                low = mid + 1;
            } else {
                high = mid;
            }
        }
        return low;
    }
}

作者：LeetCode-Solution
链接：https://leetcode.cn/problems/cuyjEf/solution/an-quan-zhong-sheng-cheng-sui-ji-shu-by-bosxd/
来源：力扣（LeetCode）
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