POJ 2352 Stars（树状数组）

                                                                 Stars

Description

Astronomers often examine star maps where stars are represented by points on a plane and each star has Cartesian coordinates. Let the level of a star be an amount of the stars that are not higher and not to the right of the given star. Astronomers want to know the distribution of the levels of the stars.

For example, look at the map shown on the figure above. Level of the
star number 5 is equal to 3 (it‘s formed by three stars with a numbers
1, 2 and 4). And the levels of the stars numbered by 2 and 4 are 1. At
this map there are only one star of the level 0, two stars of the level
1, one star of the level 2, and one star of the level 3.

You are to write a program that will count the amounts of the stars of each level on a given map.

Input

The
first line of the input file contains a number of stars N
(1<=N<=15000). The following N lines describe coordinates of stars
(two integers X and Y per line separated by a space,
0<=X,Y<=32000). There can be only one star at one point of the
plane. Stars are listed in ascending order of Y coordinate. Stars with
equal Y coordinates are listed in ascending order of X coordinate.

Output

The
output should contain N lines, one number per line. The first line
contains amount of stars of the level 0, the second does amount of stars
of the level 1 and so on, the last line contains amount of stars of the
level N-1.

Sample Input

5
1 1
5 1
7 1
3 3
5 5

Sample Output

1
2
1
1
0【分析】很常规的做法，先排序后树状数组统计。

#include <iostream>
#include <cstring>
#include <cstdio>
#include <algorithm>
#include <cmath>
#include <string>
#include <map>
#include <stack>
#include <queue>
#include <vector>
#define inf 2e9
#define met(a,b) memset(a,b,sizeof a)
typedef long long ll;
using namespace std;
const int N = 2e5+5;
const int M = 4e5+5;
int n,m,tot=0,cnt=0;
int head[N],ans[N];
int tree[33000];
struct man{
    int x,y;
    bool operator< (const man &it)const{
        if(x==it.x)return y<it.y;
        return x<it.x;
    }
}a[N];
void add(int k,int num){
    while(k<=32001){
        tree[k]+=num;
        k+=k&(-k);
    }
}
int Sum(int k){
    int sum=0;
    while(k>0){
        sum+=tree[k];
        k-=k&(-k);
    }
    return sum;
}
int main() {
    met(tree,0);met(head,-1);met(ans,0);
    scanf("%d",&n);
    for(int i=1;i<=n;i++){
        scanf("%d%d",&a[i].x,&a[i].y);
        a[i].x++;a[i].y++;
    }
    sort(a+1,a+1+n);
    for(int i=1;i<=n;i++){
        int sum=Sum(a[i].y);
        ans[sum]++;
        add(a[i].y,1);
    }
    for(int i=0;i<n;i++)printf("%d\n",ans[i]);
    return 0;
}