排序算法之归并排序

#include <iostream>
using namespace std;

void MergeArray(int a[], int begin1, int end1, int begin2, int end2)
{
	int begin = begin1;
	const int len = end2 - begin1 + 1;
	int b[len];
	int pos = 0;
	while(begin1 <= end1 && begin2 <= end2)
	{
		if(a[begin1] < a[begin2])
			b[pos++] = a[begin1++];
		else
			b[pos++] = a[begin2++];
	}
	while(begin1 <= end1) b[pos++] = a[begin1++];
	while(begin2 <= end2) b[pos++] = a[begin2++];

	for(int i = 0; i < len; ++i, ++begin)
		a[begin] = b[i];
}

void MergeSort(int a[], int begin, int end)
{
	if(begin >= end) return;
	int mid = (begin + end) / 2;
	MergeSort(a, begin, mid);
	MergeSort(a, mid + 1, end);
	MergeArray(a, begin, mid, mid + 1, end);
}

int main()
{
	int a[] = { 12, 234, 34534543, 12, 1, 464, 12,78,86};
	//int a[] = {};
	int len = sizeof(a)/sizeof(int);
	MergeSort(a, 0, len - 1);

	for(int i = 0; i < len; ++i)
		cout<< a[i] << " ";
}