POJ 2299 Ultra-QuickSort 求原始序列的逆序对数 树状数组+离散化

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

题意:给定一个序列，求这个序列的逆序数

思路：树状数组+离散化（可参考）

这个题目值得学习的便是离散化处理(数字本身不影响结果，数字的大小关系影响结果)

思想:给出一堆数字，先记录下来这些位置，然后sort排序，根据排序重新赋值。

 

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