归并排序模板

#include<iostream>
#include<algorithm>

using namespace std;

const int N = 1e5 + 10;

int a[N],tmp[N];//tmp 临时数组

void merge_sort(int* a, int l, int r) {
	if (l >= r)return;

	int mid = l + r >> 1;

	merge_sort(a, l, mid), merge_sort(a, mid + 1, r);//递归排序
	int k = 0, i = l, j = mid + 1;
	while (i <= mid && j <= r)
		if (a[i] < a[j])tmp[k++] = a[i++];
		else tmp[k++] = a[j++];
	while (i <= mid)tmp[k++] = a[i++];
	while (j <= r)tmp[k++] = a[j++];

	for (i = l, j = 0; i <= r; i++, j++)a[i] = tmp[j];//合并 从左边
}

int main()
{
	int n;
	cin >> n;

	for (int i = 0; i < n; i++)cin >> a[i];

	merge_sort(a, 0, n - 1);

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

	return 0;
}