Ultra-QuickSort

Ultra-QuickSort

Time Limit: 7000MS		Memory Limit: 65536K
Total Submissions: 44489		Accepted: 16176

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

5
9
1
0
5
4
3
1
2
3
0

Sample Output

6
0

题目大意就是让你计算一个冒泡排序中，需要交换的次数。
以为数据量较大，所以我们这里用到了Merge Sort :

#include<stdio.h>
#include<string.h>
int temp[500005] ;
int a[500005] ;
__int64 number ;
void MergeSort( int a[] , int fir , int end )
{
    int len = end - fir ;
    if( len <= 1 )
        return ;
    int mid = fir + len/2 ;
    MergeSort( a , fir , mid ) ;
    MergeSort( a , mid , end ) ;
    int p1 = fir , p2 = mid ;
    for( int i = fir ; i < end ; i++ )
    {
        if( p1 == mid )
        {
            temp[i] = a[p2++] ;
        }
        else if( p2 == end )
        {
            temp[i] = a[p1++] ;
        }
        else
        {
            if( a[p1] >= a[p2] )
            {
                temp[i] = a[p2++] ;
                number += mid - p1 ;//在Merge Sort 排序中仅仅多加了这句话
            }
            else
            {
                temp[i] = a[p1++] ;
            }
        }
    }

    for(int i = fir ; i < end ; i++ )
    {
        a[i] = temp[i] ;
    }
}
int main()
{
   // freopen("a.txt" ,"r" , stdin );
    int n ;
    while( scanf("%d" , &n ) != EOF )
    {
        if( n == 0 ) break;
        number = 0 ;
        for(int i = 0 ; i < n ; i++ )
            scanf("%d" , &a[i] ) ;
        MergeSort( a , 0 , n ) ;

        printf("%I64d\n" , number );
    }
    return 0 ;
}