hdu2689Sort it

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概述

Sort it

Time Limit: 2000/1000 MS (Java/Others) Memory Limit: 32768/32768 K (Java/Others)
Total Submission(s): 4568 Accepted Submission(s): 3171

Problem Description

You want to processe a sequence of n distinct integers by swapping two adjacent sequence elements until the sequence is sorted in ascending order. Then how many times it need.
For example, 1 2 3 5 4, we only need one operation : swap 5 and 4.

Input

The input consists of a number of test cases. Each case consists of two lines: the first line contains a positive integer n (n <= 1000); the next line contains a permutation of the n integers from 1 to n.

Output

For each case, output the minimum times need to sort it in ascending order on a single line.

Sample Input

Sample Output

  
  
   
   0

   
   6
   
   

   
   AC代码：
   
   #include <stdio.h>
#include <stdlib.h>
#include <string.h>
int tree[1001];
int lowbit(int i)
{
        return i&(-i);
}
void update(int x,int val)
{
        for(int i=x;i<1001;i+=lowbit(i))
                tree[i]+=val;
}
int Sum(int x)
{
        int sum=0;
        for(int i=x;i>0;i-=lowbit(i))
                sum+=tree[i];
        return sum;
}
int main()
{
        int n;
        while(~scanf("%d",&n))
        {
                int num;
                memset(tree,0,sizeof(tree));
                int ans=0;
                for(int i=1;i<=n;i++)
                {
                        scanf("%d",&num);
                        update(num,1);
                        ans+=i-Sum(num);
                }            
                printf("%dn",ans);
        }
        return 0;
}