164. 最大间距

给定一个无序的数组，找出数组在排序之后，相邻元素之间最大的差值。

如果数组元素个数小于 2，则返回 0。

来源：力扣（LeetCode）
链接：https://leetcode-cn.com/problems/maximum-gap
著作权归领扣网络所有。商业转载请联系官方授权，非商业转载请注明出处。

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可进一步优化，设置桶的大小为Math.min(max - min + 2, nums.length + 1);

class Solution {

    private int getBucketIndex(int min, int max, int val, int size) {
        return (int) ((long) (val - min) * size / (max - min));
    }

    public int maximumGap(int[] nums) {
        if (nums == null || nums.length < 2) {
            return 0;
        }
        int n = nums.length;
        int min = nums[0], max = nums[0];
        for (int i = 1; i < n; ++i) {
            min = Math.min(min, nums[i]);
            max = Math.max(max, nums[i]);
        }

        if (min == max) {
            return 0;
        }
        Bucket[] buckets = new Bucket[n + 1];
        for (int num : nums) {
            int index = getBucketIndex(min, max, num, n);
            if (buckets[index] == null) {
                buckets[index] = new Bucket(num, num);
            } else {
                buckets[index].min = Math.min(buckets[index].min, num);
                buckets[index].max = Math.max(buckets[index].max, num);
            }
        }
        int ans = 0;
        Bucket prev = buckets[0];
        for (int i = 1; i < buckets.length; ++i) {
            if (buckets[i] != null) {
                ans = Math.max(ans, buckets[i].min - prev.max);
                prev = buckets[i];
            }
        }

        return ans;
    }
}

class Bucket {
    int min;
    int max;

    public Bucket(int min, int max) {
        this.min = min;
        this.max = max;
    }
}