归并排序

 

示意图如下：

 

 

 

代码如下：

 

#include<iostream>

using namespace std;

void merge(int A[], int B[], int arr[], int lengthA, int lengthB)
{
	int i = 0, j = 0,count=0;
	while (count<lengthA+lengthB)
	{
		if (A[i] < B[j])
		{
			arr[count] = A[i];
				++i;
				count++;
		}
		else
		{
			arr[count] = B[j];
			++j;
			count++;
		}
		if (i == lengthA)
		{
			while (j < lengthB)
			{
				arr[count] = B[j];
				++j;
				count++;
			}
		}
		else if (j == lengthB)
		{
			while (i < lengthA)
			{
				arr[count] = A[i];
				++i;
				count++;
			}
		}

	}

}
void merge_sort(int arr[], int n)
{
	if (n > 1)
	{
		int i = n / 2;
		int j = n - n / 2;
		int *A = new int[i];
		int *B = new int[n - n / 2];
		for (int k = 0; k < i; k++)
			A[k] = arr[k];
		for (int k = 0; k < j; k++)
			B[k] = arr[i + k];
		merge_sort(A, i);
		merge_sort(B, j);
		merge(A, B, arr, i, j);
		delete []A;
		delete []B;
	}
}
void main()
{
	int arr[] = { 3, 5, 4, 6, 2, 8, 7, 9,1,10 };
	int n = sizeof(arr) / sizeof(int);
	for (int i = 0; i < n; i++)
		cout << arr[i] << " ";
	cout << endl;

	merge_sort(arr, n);
	for (int i = 0; i < n; i++)
		cout << arr[i] << " ";
	cout << endl;

	system("pause");
}