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

59105431230

Sample Output

60分析： 1.划分问题 2.递归求解. 3.合并 代码及步骤分析：

1 #include
          
            2 #include
           
             3 using namespace std; 4 const int maxn=500005; 5 int a[maxn],b[maxn]; 6 long long k; 7  8 int merge_sort(long long x,long long y) 9 {10     if(x
            
             a[j])     //找到划分后的数组左边的数大于右边的数时19             {20                 b[p++]=a[j++];//  将左边数组复制到临时空间21                 k+=m+1-i;      //注意此时k值的记录！！！22             }23             else24                 b[p++]=a[i++];   //将右边数组复制到临时空间25             26         }27         while(i<=m)28             b[p++]=a[i++];   29         while(j<=y)30             b[p++]=a[j++];31         for(i=0;i
            
           
          

归并排序时间复杂度为O（nlogn），统计改变次数k也并不改变其时间复杂度。