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 elementsuntil the sequence is sorted in ascending order. For the input sequence
Ultra-QuickSort produces the output
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.
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
树状数组求逆序数....再加个离散化
#include<cstdio>
#include<cstring>
#include<iostream>
#include<algorithm>
using namespace std;
int tree[500010];
int val[500010];
int n;
struct node
{
long long val;
int index;
}arr[500010];
int cmp(node a,node b)
{
return a.val < b.val;
}
inline int lowbit(int x)
{
return x&(-x);
}
void add(int x,int val)
{
for(int i=x;i<=n;i+=lowbit(i))
tree[i]+=val;
}
long long sum(int x)
{
long long ans=0;
for(int i=x;i;i-=lowbit(i))
ans+=tree[i];
return ans;
}
int main()
{
while(~scanf("%d",&n),n)
{
for(int i=1;i<=n;i++)
{
scanf("%d",&arr[i].val);
arr[i].index=i;
}
sort(arr+1,arr+n+1,cmp);
for(int i=1;i<=n;i++)
{
if(i==1)
val[arr[i].index]=i;
else
{
if(arr[i].val==arr[i-1].val)
val[arr[i].index]=val[arr[i-1].index];
else
val[arr[i].index]=i;
}
}
long long ans=0;
memset(tree,0,sizeof(tree));
for(int i=1;i<=n;i++)
{
add(val[i],1);
ans+=i-sum(val[i]);
}
printf("%lld\n",ans);
}
return 0;
}