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  • c#两路归并排序

制作者:剑锋冷月 单位:无忧统计网,www.51stat.net
 

/// <summary>
 /// 对目标数组进行归并排序
 /// 与QuickSort的分治比较,感受递归
 /// </summary>
 /// <param name="dest">目标数组</param>
 /// <param name="tempDest">暂存数组</param>
 /// <param name="left">当前部分左位置</param>
 /// <param name="right">当前部分右位置</param>
 /// <param name="swapTimes">当前部分中间位置</param>
 public static void TwoWayMergeSort(int[] dest, int[] tempDest, int left, int right, ref int swapTimes)
 {
 if(left < right)
 {
  int mid = (left + right) / 2;
  //分割通过递归实现
  TwoWayMergeSort(dest, tempDest, left, mid, ref swapTimes);//左一半
  TwoWayMergeSort(dest, tempDest, mid + 1, right, ref swapTimes);//右一半
  Merge(dest, tempDest, left, right, mid, ref swapTimes);//对左右各半进行归并
 }
 }
 
 /// <summary>
 /// 对当前部分进行归并
 /// </summary>
 /// <param name="dest"></param>
 /// <param name="tempDest"></param>
 /// <param name="left"></param>
 /// <param name="right"></param>
 /// <param name="mid"></param>
 /// <param name="swapTimes">逆置位置</param>
 private static void Merge(int[] dest, int[] tempDest, int left, int right, int mid, ref int swapTimes)
 {
 for(int i = left; i <= right; i ++)
  tempDest = dest;
 int index1 = left;
 int index2 = mid + 1;
 int index = left;//用left很重要,如若是0则会对dest的位置重复赋值
 //|-------|--------|
 // ^index1 ^index2,体现了归并的妙
 while(index1 <= mid && index2 <= right) 
 {
  if(tempDest[index1] <= tempDest[index2])
  {
  dest[index ++] = tempDest[index1 ++];
  }
  else
  {
  dest[index ++] = tempDest[index2 ++];
  swapTimes ++;
  }
 }
 while(index2 <= right)
 {
  dest[index ++] = tempDest[index2 ++];
 }
 while(index1 <= mid)
 {
  dest[index ++] = tempDest[index1 ++];
 }
 }



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