记录编号	118377	评测结果	AAAAAAAAAA
题目名称	数列	最终得分	100
用户昵称	HouJikan	是否通过	通过
代码语言	C++	运行时间	0.024 s
提交时间	2014-09-06 15:14:31	内存使用	1.26 MiB

#include <iostream>
#include <cstring>
#include <cstdio>
#include <cstdlib>
#include <cmath>
#include <algorithm>
#include <queue>
#include <stack>
#include <map>
#include <set>
#include <list>
#include <vector>
#include <ctime>
#include <iterator>
#include <functional>
#define pritnf printf
#define scafn scanf
#define For(i,j,k) for(int i=(j);i<=(k);(i)++)
using namespace std;
typedef long long LL;
typedef unsigned int Uint; 
const int INF=0x7ffffff;
//==============struct declaration==============

//==============var declaration=================
const int MAXN=50010;
int num[MAXN];
int sum[32768*3],n;
int l[MAXN],r[MAXN];
//==============function declaration============
int lowbit(int x);
int query(int x);
void update(int x);
//==============main code=======================
int main()
{  
  string FileName="queueb";//程序名 
  string FloderName="COGS";//文件夹名 
  freopen((FileName+".in").c_str(),"r",stdin);
  freopen((FileName+".out").c_str(),"w",stdout);
#ifdef DEBUG  
  system(("cp C:\\Users\\Administrator\\Desktop\\"+FloderName+"\\standard.cpp C:\\Users\\Administrator\\Desktop\\"+FloderName+"\\submit.txt").c_str());
  clock_t Start_Time=clock();
#endif    
  scanf("%d",&n);
  For(i,1,n)
  {
    scanf("%d",&num[i]);
    num[i]++;
  }
  memset(sum,0,sizeof(sum));
  For(i,1,n)
  {
    l[i]=query(num[i]-1);
    update(num[i]);
  }
  memset(sum,0,sizeof(sum));
  for(int i=n;i>=1;i--)
  {
    r[i]=query(num[i]-1);
    update(num[i]);
  }
  /*For(i,1,n)
    printf("%d %d\n",l[i],r[i]);*/
  LL res=0;
  For(i,1,n)
    res+=l[i]*r[i];
  printf("%lld\n",res);
#ifdef DEBUG  
  clock_t End_Time=clock();
  cout<<endl<<endl<<"Time Used: "<<(End_Time-Start_Time)/CLOCKS_PER_SEC<<endl;
#endif    
  return 0;
}
//================fuction code====================
int lowbit(int x)
{
  return x&-x;
}
int query(int x)
{
  LL res=0;
  while (x>0)
  {
    res+=sum[x];
    x-=lowbit(x);
  }
  return res;
}
void update(int x)
{
  while (x<=32767)
  {
    sum[x]++;
    x+=lowbit(x);
  }
}