POJ1542 Ultra-QuickSort

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

59105431230

Sample Output

6

0

#include<stdio.h>#include<algorithm>#include<string.h>using namespace std;pair<int,int>v[500005];int dp[500004],a[500005],b[500005];int bit[500005+1],n;int sum(int i);void add(int i,int x);int main(){int i,j,k;while(scanf("%d",&n),n!=0){for(i=0;i<n;i++){scanf("%d",&v[i].first);v[i].second=i;}sort(v,v+n);b[0]=1;a[v[0].second]=1;for(i=1;i<n;i++){if(v[i].first>v[i-1].first)b[i]=b[i-1]+1;elseb[i]=b[i-1];a[v[i].second]=b[i];}memset(bit,0,sizeof(bit));long long ans;ans=0;for(i=0;i<n;i++){ans+=i-sum(a[i]);add(a[i],1);}printf("%lld\n",ans);}return 0;}int sum(int i){int s=0;while(i>0){s+=bit[i];i-=i& -i;}return s;}void add(int i,int x){while(i<=n){bit[i]+=x;i+=i & -i;}}