# Tree-like array LA 4329 Asian Games Beijing Division

Source: Internet
Author: User

Review the tree-like array

It's a pretty interesting question:

Http://uva.onlinejudge.org/index.php?option=com_onlinejudge&Itemid=8&category=501&page=show_ problem&problem=4174

Learn a few things:
1. Construction of tree-like array c[i], a c[i]=s[i]-s[i-lowbit (i)]; This is a practice that has been used. Now learn a new, direct add (I,a[i]), and (S[i] for a to A[i)

2, prefixes and ideas, the sum of the tree array itself is based on the idea of prefix and. The number of numbers smaller than a certain number, by opening a large number of space + suffix array, efficient statistics out of a number of small number

3, in fact, I think through this question. The ability to make an O (nlogn) sorting algorithm. Of course, the place that is not good is only can be whole number, but should be able to solve with vector+map?

Stick to your own code first. , because the code behind the LRJ Daniel is too concise ...

`#include <iostream> #include <cstdio> #include <cstring> #include <algorithm> #include < Queue> #include <functional>using namespace std; #define MAXN 20010#define SIZE 100015int a[maxn],sma[size],c[ Size],s[size],e[size],tot[size];int n,mmax;int lowbit (int i) {return I & (-i);}    int sum (int i) {int ans=0;    for (; I>0;i-=lowbit (i)) ans+=c[i];  return ans;}    void Add (int x, int d) {while (x <= SIZE) {c[x] + = D; x + = Lowbit (x);        }}void Init () {memset (c,0,sizeof (c));        memset (A,0,sizeof (a));        memset (sma,0,sizeof (SMA));        Memset (s,0,sizeof (s));        memset (E,0,sizeof (e)); memset (tot,0,sizeof (TOT));}    int main () {//freopen ("La4329.txt", "R", stdin);    int t;    Long long ans;    scanf ("%d", &t);        while (t--) {mmax=0;        ans=0;        Init ();        scanf ("%d", &n);            for (int i=1;i<=n;i++) {scanf ("%d", &a[i]);      Mmax=max (Mmax,a[i]);      Add (a[i],1);            C[i]=sum (a[i]-1);            E[a[i]]=1;        Sma[a[i]]=sum (a[i]-1);        } memset (C,0,sizeof (c));            for (int i=1;i<=mmax;i++) {s[i] =s[i-1]+e[i];            C[i]=s[i]-s[i-lowbit (i)];        Tot[i]=sum (i-1); }/////////////////////////for (int i=1;i<=n;i++)//{//printf ("sma[a[%d]" =%d tot (%d        ) =%d\n ", I,sma[a[i]],a[i],tot[a[i]]); }///////////////////////for (int i=1;i<=n;i++) {int tmp = Tot[a[i]]-sma[a[i]];/*a[i        ] The number of smaller than a[i] */ans+= (Long Long) tmp* (I-1-sma[a[i]) + (Long Long) sma[a[i]]* (n-i-tmp);    } printf ("%lld\n", ans); } return 0;}`

Standard process

`LA4329 Ping pong//Rujia liu#include<cstdio> #include <vector>using namespace std;//inline int lowbit (int x {return x& (x^ (x-1));} inline int lowbit (int x) {return x&-x;}  struct Fenwicktree {int n;  Vector<int> C; void Resize (int n) {this->n = n; C.resize (n);  } void Clear () {Fill (C.begin (), C.end (), 0);} // ????    A+a+...+a[x] (x<=n) int sum (int x) {int ret = 0;    while (x > 0) {ret + = c[x]; x-= Lowbit (x);  } return ret;    }//a[x] + = d (1<=x<=n) void Add (int x, int d) {while (x <= N) {c[x] + = D; x + = Lowbit (x); }}};const int maxn = 20000 + 5;int N, A[maxn], C[MAXN], D[MAXN];  Fenwicktree F;int Main () {freopen ("La4329.txt", "R", stdin);  int T;  scanf ("%d", &t);    while (t--) {scanf ("%d", &n);    int Maxa = 0;    for (int i = 1; I <= n; i++) {scanf ("%d", &a[i]), Maxa = Max (Maxa, A[i]);}    F.resize (MAXA);    F.clear ();    for (int i = 1; I <= n; i++) {F.add (a[i], 1);  C[i] = f.sum (a[i]-1);    } f.clear ();      for (int i = n; I >= 1; i--) {F.add (a[i], 1);    D[i] = f.sum (a[i]-1);    } long long ans = 0;    for (int i = 1; I <= n; i++) ans + = (long Long) c[i]* (N-i-d[i]) + (Long Long) (i-c[i]-1) *d[i];  printf ("%lld\n", ans); } return 0;}`

Tree-like array LA 4329 Asian Games Beijing Division

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