Poj 2299 - Ultra-QuickSort 离散化,树状数组,逆序对

Ultra-QuickSort

Time Limit: 7000MS		Memory Limit: 65536K
Total Submissions: 52306		Accepted: 19194

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

Source

Waterloo local 2005.02.05

 

题意：给定n个数，只能交换相邻的两个元素，至少交换几次，成为递增序列。

题解：

明显要求序列的逆序对数目。。。

对于样例：

5

9 1 0 5 4

我们将其排序：

0 1 4 5 9

在每个位置上初始放为1.

1 1 1 1 1

然后，从原序列开始遍历。

先到9，我们把其排好序的位置拿出，即为5。

然后统计位置5之前有多少1。

1 1 1 1 1

————  > 4个  ans+=4

然后把5号位置放为0。

1 1 1 1 0

继续操作即可。。。

这个树状数组维护即可。。。

注意开long long和原序列排序后要去重。。。

 #include<bits/stdc++.h>
 using namespace std;
 #define MAXN 500010
 #define LL long long
 int n,BIT[MAXN],a[MAXN],aa[MAXN];
 int read()
 {
     int s=,fh=;char ch=getchar();
     while(ch<''||ch>''){if(ch=='-')fh=-;ch=getchar();}
     while(ch>=''&&ch<=''){s=s*+(ch-'');ch=getchar();}
     return s*fh;
 }
 int Lowbit(int o){return o&(-o);}
 void Update(int o,int o1)
 {
     while(o<=n)
     {
         BIT[o]+=o1;
         o+=Lowbit(o);
     }
 }
 int Sum(int o)
 {
     int sum=;
     while(o>)
     {
         sum+=BIT[o];
         o-=Lowbit(o);
     }
     return sum;
 }
 int main()
 {
     int tot,i,wz;
     LL ans;
     while()
     {
         n=read();if(n==)break;
         for(i=;i<=n;i++){a[i]=read();aa[i]=a[i];}
         memset(BIT,,sizeof(BIT));
         sort(a+,a+n+);
         tot=unique(a+,a+n+)-(a+);
         for(i=;i<=tot;i++)Update(i,);
         ans=;
         for(i=;i<=n;i++)
         {
             wz=lower_bound(a+,a+tot+,aa[i])-a;
             ans+=(LL)Sum(wz-);
             if(BIT[wz]!=)Update(wz,-);
         }
         printf("%lld\n",ans);
     }
     fclose(stdin);
     fclose(stdout);
     return ;
 }