C++_归并排序

//合并有序数组

//合并例子

void MemeryArray(int a[], int n, int b[],int m, int c[])
{
	int i,j,k;

	i=j=k=0;

	while(i<n && j<m)
	{
		if(a[i]<b[j])
		{
			c[k++] = a[i++];
		}
		else
		{
			c[k++]=b[j++];
		}
	}

	while(i<n)
	{
		c[k++]=a[i++];
	}
	while(j<n)
	{
		c[k++] = b[j++];
	}

}

//排序需要调用的如下

//排序调用

bool MergeSort(int a[], int n)
{
	int *p = new int[n];

	if(p==NULL)
	{
		return false;
	}

	mergesort(a,0,n-1,p);  //用n-1是因为 合并的时候用的是 "<=" 而不是 "<"

	delete[] p;

	return true;
}

//数组按照中值，左右执行递归

void mergesort(int a[],int first,int last,int temp[])
{
	if(first<last)
	{
		int mid = (first+last)/2;
		mergesort(a,first,mid,temp);
		mergesort(a,mid+1,last,temp);
		mergearray(a,first,mid,last,temp);

	}
}

//最后对数组进行合并

void mergearray(int a[], int first, int mid, int last, int temp[])
{
	int i=first, j = mid+1;
	int m = mid, n =last;
	int k=0;

	while(i<=m&&j<=n)
	{
		if(a[i]<=a[j])
		{
			temp[k++]=a[i++];
		}
		else
		{
			temp[k++] = a[j++];
		}
	}
	while(i<=m)
	{
		temp[k++] = a[i++];
	}
	while(j<=n)
	{
		temp[k++]=a[j++];
	}

	for(i=0;i<k;i++)
	{
		a[first+i] = temp[i];
	}
}