1、归并排序
归并排序(MERGE-SORT)是利用归并的思想实现的排序方法,该算法采用经典的分治(divide-and-conquer)策略(分治法将问题分(divide)成一些小的问题然后递归求解,而治(conquer)的阶段则将分的阶段得到的各答案"修补"在一起,即分而治之)。
转载:https://www.cnblogs.com/chengxiao/p/6194356.html
2、具体分析
3、代码实现
/*
作者:kimicr
时间:20200327
功能:归并排序
特点:稳定且占内存时间复杂度【nlogn】
*/
#include"iostream"
using namespace std;
void Merge(int *arr, int start, int mid, int end)
{
int N = end - start + 1;//临时数组存合并后的有序序列
int* tmp = new int[N];
for (int k = start; k <= end; k++)
tmp[k - start] = arr[k];
int left = start;
int right = mid + 1;
for (int step = start; step <= end; step++)
{
if (left > mid)
{
arr[step] = tmp[right - start];
right++;
}
else if (right > end)
{
arr[step] = tmp[left - start];
left++;
}
else if (tmp[left - start] <= tmp[right - start])
{
arr[step] = tmp[left - start];
left++;
}
else
{
arr[step] = tmp[right - start];
right++;
}
}
/*int i = 0;
int left = start;
int right = mid + 1;
while (left <= mid && right <= end)
tmp[i++] = arr[left] <= arr[right] ? arr[left++] : arr[right++];
while (left <= mid)
tmp[i++] = arr[left++];
while (right <= end)
tmp[i++] = arr[right++];
for (int j = 0; j<N; ++j)
arr[start + j] = tmp[j];*/
delete[] tmp;//删掉堆区的内存
}
void MergeSort(int *array, int start, int end)
{
if (start == end)
return; //递归基是让数组中的每个数单独成为长度为1的区间
int mid = (start + end) / 2;
MergeSort(array, start, mid);
MergeSort(array, mid + 1, end);
Merge(array, start, mid, end);
int main()
{
int a[] = {
20, 17, 8, 7, 16, 3};
MergeSort(a, 0, 5);
for (int i = 0; i < (sizeof(a)/sizeof(a[0])); i++)
cout << a[i] << " ";
cout << endl;
system("pause");
return 0;
}
}