歸併排序

1.兩個有序序列合併核心思想

 對兩個有序的序列進行合併  不斷選兩組第一個，選中的數  
① 那組的指示器後移 
② 數放入新的序列 

a[] = { 3,6 }; b[] = { 1,2 ,9 };

2.兩個有序序列合併程式碼

void Merge(Rectype R[], int Low, int Mid, int High)
{
 int i = Low, j = Mid + 1, k = 0;  //K是用來存資料的下標，i,j為兩端需要合併的下標
 Rectype *RTemp = (Rectype *)malloc((High - Low +
 
 1) * sizeof(Rectype));
 while (i < Mid && j < High)
 {
  if (R[i].Key < R[j].Key)
   RTemp[k++] = R[i++];
  else
   RTemp[k++] = R[j++];
 }
 while (i < Mid) RTemp[k++] = R[i++];//對剩餘元素排序
 while (j < High) RTemp[k++] = R[j++];
 for (k = 0, i = Low; i <= High; k++, i++) R[i] = RTemp[
 
k];  //複製到原陣列
 free(RTemp);  //銷燬
}

自上而下的歸併排序程式碼

void MergeSort(Rectype R[], int Low, int High)
{
 int Mid;
 if (Low < High)
 {
  Mid = (Low + High) / 2;
  MergeSort(R, Low, Mid);
  MergeSort(R, Mid + 1, High);
  Merge(R, Low, Mid, High);
 }
}