POJ 3928 Ping Pong (tree-like array) _poj

Each person has a unique ranking (number size) with a unique position (from the back of the line), to meet the rank between the two and the position is also between the number of ternary groups

Train of thought: enumerating which numbers in between can only be used in O (n^3) time is too high, but can change the mind. We can convert to each number a, and find each number B that is larger than the current number a. After the number B is larger than the current number of B C, and then for each a corresponding to the number of C in each B of the sum is half the result, of course, compared to the other half of the method is similar. In fact, the tree-like array for the first time to find each B, and then use B to find C, so that two times is good

#include <set> #include <map> #include <queue> #include <stack> #include <cmath> #include <vector> #include <string> #include <cstdio> #include <cstring> #include <stdlib.h> #
Include<iostream> #include <algorithm> using namespace std; #define EPS 1E-8/* Note that there may be output -0.000*/#define SGN (x) (x<-eps? -1:x<eps? 0:1)//x to a comparison of two floating-point numbers, note that the integer #define CVS (x) (x &G T 0.0? X+EPS:X-EPS)//floating-point number conversion #define ZERO (x) ((x) >0? (
x):-(x) <eps)//Determine whether equals 0 #define MUL (a,b) (a<<b) #define DIR (a,b) (A&GT;&GT;B) typedef long Long LL;
typedef unsigned long long ull;
const INT inf=1<<28;
Const double Pi=acos (-1.0);
const int mod=1e9+7;
const int max=20010; struct node {int val,pos;}
Num[max];
int n;
ll Bit[max];
        int lowbit (int x) {return x& (-X);} void Add (int x,int y) {while (x<=n) {bit[x]+= (ll) y;
    X+=lowbit (x);
} return;
    ll Sum (int x) {ll sum=0ll; while (x>0) {sUM+=BIT[X];
    X-=lowbit (x);
return sum;
    ll Manx (int n,int *pop,int *ivsn,int *ivsn2,int hh) {ll sum=0ll,manx=0ll;
    memset (bit,0ll,sizeof (bit));
        for (int i=n;i>0;--i) {if (HH) ivsn[i]=sum-sum (Pop[i]);
        else Ivsn[i]=sum (Pop[i]);
        ADD (Pop[i],ivsn2[i]);
        Sum+=ivsn2[i];
    Manx+=ivsn[i];
return Manx;
int Pop[max],ivsn[max],ivsn2[max];
    BOOL CMP (struct node p1,struct node p2) {return p1.val<p2.val;} int main () {int t;
    ll ans;
    scanf ("%d", &t);
        while (t--) {ans=0ll;
        scanf ("%d", &n);
            for (int i=1;i<=n;++i) {scanf ("%d", &num[i].val);
            Num[i].pos=i;
        Ivsn2[i]=1;
        Sort (num+1,num+n+1,cmp); for (int i=1;i<=n;i++) pop[num[i].pos]=i;//discretization Manx (n,pop,ivsn,ivsn2,1);//Find the IVSN of each of the pop arrays after each number larger than the current one
        The sum of 2 array values Ans+=manx (n,pop,ivsn2,ivsn,1); for (int i=1;i<=n;i++) Ivsn2[i]=1;
        Manx (n,pop,ivsn,ivsn2,0)//Find the sum of the IVSN2 array values for each number of pop arrays later than the current small one Ans+=manx (n,pop,ivsn2,ivsn,0);
    printf ("%i64d\n", ans);
return 0;
 }