Ultra-QuickSort——归并排序

最新推荐文章于 2020-12-16 18:34:13 发布

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本文详细解析了Ultra-QuickSort算法，一种基于归并排序的高效排序方法。通过分析其工作原理，展示了如何计算排序特定输入序列所需的最少交换次数，并提供了完整的C++代码实现。

Description

In this problem, you have to analyze a particular sorting algorithm. The algorithm processes a sequence of n distinct integers by swapping two adjacent sequence elements until the sequence is sorted in ascending order. For the input sequence

9 1 0 5 4 ,

Ultra-QuickSort produces the output

0 1 4 5 9 .

Your task is to determine how many swap operations Ultra-QuickSort needs to perform in order to sort a given input sequence.

Input

The input contains several test cases. Every test case begins with a line that contains a single integer n < 500,000 -- the length of the input sequence. Each of the the following n lines contains a single integer 0 ≤ a[i] ≤ 999,999,999, the i-th input sequence element. Input is terminated by a sequence of length n = 0. This sequence must not be processed.

Output

For every input sequence, your program prints a single line containing an integer number op, the minimum number of swap operations necessary to sort the given input sequence.

Sample Input

Sample Output

6
0

#include <cstdio>
#include <cstring>
#include <string>
#include <iostream>
#include <algorithm>
using namespace std;
long long int a[500010],temp[500010];
long long int ans,n;
void mergearray(int s,int e){ 
	if(s==e) //等于退出 
		return;
	int i;
	int mid=(s+e)>>1;//右移，相当于（s+e）/2 
	int l=s, r=mid+1, k=s;
	while(l<=mid&&r<=e){
		if(a[l]<=a[r]){
			temp[k]=a[l++];
		} else {
			temp[k]=a[r++];
			ans+=mid-l+1;//需要移动的位移差 
		}
		k++;
	}
	//把遗漏的加到数组里 
	while(l<=mid) 
		temp[k++]=a[l++];
	while(r<=e) 
		temp[k++]=a[r++];
	for(i=s;i<=e; i++) 
		a[i]=temp[i];
	return ;
}
void sortd(int s,int e){
	if(s>=e) 
		return;
	int mid=(s+e)>>1;
	sortd(s,mid);//左递归合并 
	sortd(mid+1,e);//右递归合并 
	mergearray(s,e);//合并细化（排序）后的数组 
	return;
}
int main(){
	int i,j,k;
	while(~scanf("%d",&n) && n){
		ans=0;
		for(i=1;i<=n;i++){
			scanf("%lld",&a[i]);
		}
		sortd(1,n);
		printf("%lld\n",ans);
	}
	return 0;
}

一个很好的归并排序https://blog.youkuaiyun.com/MoreWindows/article/details/6678165