18-基数排序

package cn.sun.it.review;

import java.util.Arrays;

public class RadixSort {

    public static void main(String[] args) {
        int[] arr = {278,109,63,930,589,184,505,269,8,83};
        int[] sort = sort(arr);
        System.out.println(Arrays.toString(sort));
    }

    public static int[] sort(int[] sourceArray) {
        int[] arr = Arrays.copyOf(sourceArray, sourceArray.length);
        int maxDigit = getMaxDigit(arr);
        return radixSort(arr, maxDigit);
    }

    private static int getMaxDigit(int[] arr) {
        int maxValue = getMaxValue(arr);
        return getNumLength(maxValue);

    }

    private static int getMaxValue(int[] arr) {
        int maxValue = arr[0];
        for (int value : arr) {
            if (maxValue < value) {
                maxValue = value;
            }
        }
        return maxValue;
    }

    private static int getNumLength(long num) {
        if (num == 0) {
            return 1;
        }
        int length = 0;
        for (long temp = num; temp != 0; temp /= 10) {
            length++;
        }
        return length;
    }

    private static int[] radixSort(int[] arr, int maxDigit) {
        int mod = 10;
        int dev = 1;
        for (int i = 0; i < maxDigit; i++, dev *= 10, mod *= 10) {
            int[][] counter = new int[mod*2][0];
            for(int j=0;j<arr.length;j++){
                int bucket = ((arr[j]%mod)/dev)+mod;
                counter[bucket] = arrayAppend(counter[bucket],arr[j]);
            }
            int pos =0;
            for(int[] bucket : counter){
                for(int value : bucket){
                    arr[pos++] = value;
                }
            }
        }
        return arr;
    }

    private static int[] arrayAppend(int[] arr, int value) {
        arr = Arrays.copyOf(arr, arr.length+1);
        arr[arr.length-1] = value;
        return arr;
    }
}