归并排序

import java.math.* ;import java.util.* ;/** *  */public class Test extends Base{public static void main(String[] args) throws Exception{int[] arr = getRandomArr() ;println(arr); int[] temp = new int[arr.length] ;mergeSort(arr , arr.length);println(arr);println();}public static void mergeSort(int[] arr , int n) throws Exception{int[] temp = new int[n] ;divideSort(arr, 0 , n - 1 , temp);}public static void divideSort(int[]arr , int first , int last , int[] temp) throws Exception{if(first <  last){divideSort(arr , first, (first + last) / 2 , temp);divideSort(arr , (first + last) / 2 + 1 , last , temp);mergeArray(arr, first , (first + last) / 2 , last , temp);}}public static void mergeArray(int[] arr ,int first, int mid , int last , int[] temp){int firstStart = first , firstEnd = mid ;int secondStart = mid + 1 , secondEnd = last ;int k = 0 ;while (firstStart <= firstEnd && secondStart <= secondEnd){if(arr[firstStart] < arr[secondStart])temp[k++] = arr[firstStart++] ;else temp[k++] = arr[secondStart++] ;}while(firstStart <= mid)temp[k++] = arr[firstStart++] ;while(secondStart <= last)temp[k++] = arr[secondStart++] ;for (int i = 0; i < k ; i++ ){arr[first + i] = temp[i] ;}}}