POJ 2352 Stars (树状数组)

题意：给定一组点，问二维空间中各个点的等级是多少，点的等级定义如下：其左下方点的个数。

思路：昨天看了树状数组，然后怀着无比激动的心情开始了，一阵子思考--不会，在一阵子思考--还是不会，只能硬着头皮翻报告......终于明白树状数组是怎么应用了....汗了....到现在才开始学树状数组....不管怎么说，树状数组的确是一个强大的在线数据结构！

#include <iostream>
#include <cstdio>
#include <algorithm>
#include <memory.h>
#include <cmath>
#include <ctime>
#include <bitset>
#include <queue>
#include <vector>
using namespace std;

const int BORDER = (1<<20)-1;
const int MAXSIZE = 37;
const int MAXN = 40000;
const int INF = 1000000000;
#define CLR(x,y) memset(x,y,sizeof(x))
#define ADD(x) x=((x+1)&BORDER)
#define IN(x) scanf("%d",&x)
#define OUT(x) printf("%d\n",x)
#define MIN(m,v) (m)<(v)?(m):(v)
#define MAX(m,v) (m)>(v)?(m):(v)
#define ABS(x) ((x)>0?(x):-(x))

int tre[MAXN],ans[MAXN],arr[MAXN];
int n_tre,n;

int init()
{
    CLR(tre,0);
    CLR(ans,0);
    CLR(arr,0);
    n_tre = MAXN;
    return 0;
}
int lowbit(int x)
{
    return x&(-x);
}
void modify(int ind,int delta)
{
    while( ind <= n_tre)
    {
        tre[ind] += delta;
        ind += lowbit(ind);
    }
}
int get_sum(int ind)
{
    int sum = 0;
    while(ind != 0)
    {
        sum += tre[ind];
        ind -= lowbit(ind);
    }
    return sum;
}
int work()
{
    int i,b,a,j,tmp;
    for(i = 0; i < n; ++i)
    {
        scanf("%d%d",&a,&b);
        ++a;
        ++ans[get_sum(a)];
        modify(a,1);
    }
    for(i = 0; i < n; ++i)
        OUT(ans[i]);
    return 0;
}
int main()
{
    while(IN(n)!=EOF)
    {
        init();
        work();
    }
    return 0;
}