排序：多线程版本的归并排序

多线程版本的归并排序

这里的TR和TR2都无需加锁，因为每个Msort处理的数据段都是不一样的。

#include 
#include 
#include 


using namespace std;

void merge(vector<int> TR2, vector<int>& TR, int left, int mid, int right)
{
    int i = left, j = mid + 1, a = left;

    for(; i <= mid && j <= right; )
    {
        if(TR2[i] <= TR2[j]) TR[a++] = TR2[i++];
        else TR[a++] = TR2[j++];
    }
    while(i <= mid) TR[a++] = TR2[i++];
    while(j <= right) TR[a++] = TR2[j++];
    return;
}


void Msort(vector<int> SR, vector<int>& TR, int left, int right)
{
	if (left == right)
	{
		TR[left] = SR[left];
		return;
	}
	vector<int> TR2(SR.size(), 0);
	int mid = (left + right) >> 1;

	thread one(Msort, SR,  std::ref(TR2), left, mid);
	thread two(Msort, SR,  std::ref(TR2), mid + 1, right);

    one.join();
    two.join();
	merge(TR2, TR, left, mid, right);
}



int main(){
    vector<int> test = {2,3,1,6,8,10,20,4,7};
    Msort(test, test, 0, static_cast<int>(test.size()) - 1);
    for(int i = 0; i < test.size(); i++)
        cout << test[i] << endl;
    return 0;

}