归并排序

视频链接：https://www.bilibili.com/video/av9982752?from=search&seid=12418703498405255943

参考代码：

#include<cstdio>
#include<iostream>
using namespace std;
const int maxn = 100005;
int n;
int a[maxn];
void merge(int L, int M, int R)
{
	const int Sizeof_Left = M - L + 1;
	const int Sizeof_Right = R - M;
	int *left=new int[Sizeof_Left];
	int *right=new int [Sizeof_Right];
	for (int i = L; i <= M; i++)
		left[i - L] = a[i];
	for (int i = M + 1; i <= R; i++)
		right[i - M - 1] = a[i];

	int i = 0;
	int j = 0;
	int k = L;
	while (i < Sizeof_Left&&j < Sizeof_Right)
	{
		if (left[i] < right[j])
		{
			a[k] = left[i];
			i++;
			k++;
		}
		else
		{
			a[k] = right[j];
			j++;
			k++;
		}
	}
	while (i < Sizeof_Left) a[k++] = left[i++];
	while (j < Sizeof_Right) a[k++] = right[j++];
}
void mergesort(int L, int R)
{
	if (L == R) return;

	int M = (L + R) /2;
	mergesort(L, M);
	mergesort(M + 1, R);
	merge(L, M, R);
}
int main()
{
	printf("输入数组大小：
");
	cin >> n;
	printf("输入数组元素: 
");
	for (int i = 0; i < n; i++)
		scanf("%d", &a[i]);
	mergesort(0, n - 1);
	printf("归并排序后结果： 
");
	for (int i = 0; i < n; i++)
		printf("%d ", a[i]);
	printf("
");
	return 0;
}