計數排序

import java.math.* ;
import java.util.* ;

/**
 * 
 */
public class Test extends Base{
	public static void main(String[] args) throws Exception{
		int[] arr = getRandomArr() ;
		println(arr);  
		countingSort(arr , arr.length );
		println(arr);
		println();		
	}

	public static void countingSort(int[] arr, int n){
		int maxValue = arr[0] ;
		for (int i =0; i < n ; i++){
			if (arr[i] > maxValue){
				maxValue = arr[i] ;
			}
		}
		int[] count = new int[maxValue+1] ;
		int[] temp = new int[n] ;
		for (int i = 0 ; i < n ; i++){
			count[arr[i]]++ ; ;
		}
		for (int i = 1; i < count.length ; i++){
			count[i] = count[i] + count[i - 1] ;
		} 
		for (int i = n - 1; i >= 0; i-- ){
			temp[count[arr[i]] - 1] = arr[i] ;
			count[arr[i]]-- ; 
		}
		for (int i = 0 ; i < n ; i++){
			arr[i] = temp[i] ;
		}
		
	}

}