poj2299

Ultra-QuickSort

Time Limit: 7000MS		Memory Limit: 65536K
Total Submissions: 51330		Accepted: 18828

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

代码：

#include<cstdio>
#include<cstring>
#include<algorithm>
#define ll __int64
using namespace std;
const int N=500005;
int n;
int bit
;int aa
;
struct node{
int ord,val;
}st
;

bool cmp(node n1,node n2){
return n1.val<n2.val;
}

int lowbit(int n){
return n&-n;
}

ll sum(int x){
ll res=0;
while(x>0){
res+=bit[x];
x-=lowbit(x);
}
return res;
}

void add(int x,int d){
while(x<=n){
bit[x]+=d;
x+=lowbit(x);
}
}

int main()
{
while(scanf("%d",&n)&&n!=0)
{
memset(bit,0,sizeof(bit));
//离散化
for(int i=1;i<=n;i++){
scanf("%d",&st[i].val);
st[i].ord=i;
}
sort(st+1,st+n+1,cmp);
for(int i=1;i<=n;i++) aa[st[i].ord]=i;
//求逆序数
ll ans=0;
for(int i=1;i<=n;i++){
add(aa[i],1);
ans+=i-sum(aa[i]);
}
printf("%I64d\n",ans);
}
return 0;
}