Solution.cs

using System;
using System.Linq;

public class Solution {
    public int MaximumGap(int[] nums) {
        if (nums.Length < 2) return 0;
        var max = nums.Max();
        var min = nums.Min();
        var bucketSize = Math.Max(1, (max - min) / (nums.Length - 1));
        var buckets = new Tuple<int, int>[(max - min) / bucketSize + 1];
        foreach (var num in nums)
        {
            var index = (num - min) / bucketSize;
            if (buckets[index] == null)
            {
                buckets[index] = Tuple.Create(num, num);
            }
            else
            {
                buckets[index] = Tuple.Create(Math.Min(buckets[index].Item1, num), Math.Max(buckets[index].Item2, num));
            }
        }

        var result = 0;
        Tuple<int, int> lastBucket = null;
        for (var i = 0; i < buckets.Length; ++i)
        {
            if (buckets[i] != null)
            {
                if (lastBucket != null)
                {
                    result = Math.Max(result, buckets[i].Item1 - lastBucket.Item2);
                }
                lastBucket = buckets[i];
            }
        }
        return result;
    }
}