基数排序

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基数排序，是基于计数排序的稳定排序。对于元素的每一位进行排序，例如十进制的101,100，111从个位先计数排序，再十位计数排序，最后百位上计数排序。

当然也并一定是按十进制来进行排序，可以按任何进制进行排序。

时间复杂度为O(k * n)，k为位数；空间复杂度为O(radix + n)，radix为计数所用的桶，比如10进制为10，十六进制为16。

golang代码如下：

package algorithmsfunc RadixSort(slice []int, countBase, divideLength int) {sortMap := divideSlices(slice, countBase, divideLength)//sortMap := make(map[int]int)for index := 0; index != divideLength; index ++ {countSortWithMap(sortMap, countBase, slice, index)}}func divideSlices(slice []int, countBase, divideLength int)(sortMap map[int][]int) {sortMap = make(map[int][]int, len(slice))for _, value := range slice {sortMap[value] = getSliceFromInt(value, countBase, divideLength)[:divideLength]}return sortMap}func getSliceFromInt(num, countBase int, divideLength int)(divideSlice []int) {divideSlice = make([]int, divideLength)for i := 0; num != 0; i ++ {divideSlice[i] = num % countBasenum = num / countBase}return divideSlice}func countSortWithMap(sortMap map[int][]int, countBase int, keySlice []int, index int) {slice := getIndexSlice(sortMap, keySlice, index)countSortWithSlice(slice, keySlice, countBase)}func getIndexSlice(sortMap map[int][]int, keySlice []int, index int)(slice []int) {slice = make([]int, len(keySlice))for i, v := range keySlice {slice[i] = sortMap[v][index]}return slice}func countSortWithSlice(slice []int, keySlice []int, countBase int) {indexSlice := make([]int, countBase)for _, v := range slice {indexSlice[v]++}for i := 0; i != countBase - 1; i++ {indexSlice[i + 1] += indexSlice[i]}sortedSlice:= make([]int, len(slice))for reverseIndex := len(keySlice) - 1; reverseIndex >= 0; reverseIndex-- {indexSlice[slice[reverseIndex]]--sortedSlice[indexSlice[slice[reverseIndex]]] = keySlice[reverseIndex]}for i, _ := range slice {keySlice[i] = sortedSlice[i]}}

测试代码即main包代码：

package mainimport ("algorithms""fmt")func main() {slice := []int{100, 4, 2, 33, 555, 2, 101, 200, 2, 73, 27, 26, 89, 201, 1001, 500, 201, 451, 6110}algorithms.RadixSort(slice, 16, 4)fmt.Println(slice)}

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