算法实践篇-基于计数排序的基数排序

package com.sort;

public class RadixSort {
  public static int[] radixSort(int [] data,int d){
    int []source=new int[data.length];
    int []target=new int[data.length];
    for(int i=0;i<d;i++){
      for(int j=0;j<data.length;j++){
        source[j]=buildBitValue(data[j],i);
      }
      countingSort(data,source,target);
      data=target;
      target=new int[data.length];
    }
    return data;
  }
  
  private static int buildBitValue(int value,int i){
    if(i==0){
      return value%((int)Math.pow(10, i+1));
    }else{
      return (value/((int)Math.pow(10, i)))%10;
    }
  }
  
  public static void countingSort(int []full,int []source,int[]target){
    int k=10;
    int[] c=new int[k];
    for(int i=0;i<source.length;i++){
      c[source[i]]=c[source[i]]+1;
    }
    for(int i=1;i<k;i++){
      c[i]=c[i]+c[i-1];
    }
    for(int i=source.length-1;i>=0;i--){
      target[c[source[i]]-1]=full[i];
      c[source[i]]=c[source[i]]-1;
    }
  }
  
  public static void main(String[] args) {
    int [] data=new int[]{11,41,31,81,11,61,19};
    for(int i=0;i<data.length;i++){
      System.out.print(data[i]+" ");
    }
    System.out.println();
    data=radixSort(data,2);
    for(int i=0;i<data.length;i++){
      System.out.print(data[i]+" ");
    }
    System.out.println();

  }

}