桶排序（Bucket sort）原理是将数组分到有限数量的桶里，然后
寻访序列，并且把项目一个一个放到对应的桶子去，对每个不是空的桶子进行排序，最终将所有的桶合并.
核心代码:
<pre><code>` func sort(arr:inout [Int],min:Int,max:Int,gap:Int) {

    var bucketlist:[[Int]] = []
    let bucketCount:Int = (max - min) / gap + 1
    
    // 建桶
    for _ in 0..<bucketCount {
        let temp:[Int] = []
        bucketlist.append(temp)
    }
    
    // 分桶
    for i in 0..<arr.count {
        let index:Int = (arr[i] - min) / gap
        bucketlist[index].append(arr[i])
    }
    
    // 小桶排序
    for i in 0..<bucketCount {
        if bucketlist[i].count > 0 {
            buketInnerSort(arr: &bucketlist[i])
        }
    }
    
    var index:Int = 0
    for i in 0..<bucketCount {
        var bucket:[Int] = bucketlist[i]
        if bucket.count > 0 {
            for j in 0..<bucket.count {
                arr[index] = bucket[j]
                index += 1
            }
        }
    }
    
}

private func buketInnerSort(arr:inout [Int])  {
    let count:Int = arr.count
    for i in 1..<count {
        for j in (1...i).reversed() {
            if arr[j] < arr[j-1] {
                swap(&arr[j], &arr[j-1])
            }
        }
    }
}`</code></pre>

测试代码:
<pre><code>let bucketSort:BucketSort = BucketSort() var arr:[Int] = [-10, -9, -20, 29, 25, 3, 49, 9, 37, 21, 43] bucketSort.sort(arr: &arr, min: -20, max: 50, gap: 10) print("FlyElephant--桶排序---\(arr)")</code></pre>