POJ2352_Stars(线段树/单点更新)

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解题报告

题意：

坐标系中，求每颗星星的左下角有多少星星。

思路：

把横坐标看成区间，已知输入是先对y排序再对x排序，每次加一个点先查询该点x坐标的左端有多少点，再更新点。

#include <iostream>
#include <cstdio>
#include <cstring>

using namespace std;
int sum[200000];
struct node {
    int x,y;
} p[20000];
void push_up(int root) {
    sum[root]=sum[root*2]+sum[root*2+1];
}
void update(int root,int l,int r,int p,int v) {
    int mid=(l+r)/2;
    if(l==r) {
        sum[root]++;
        return;
    }
    if(p<=mid)update(root*2,l,mid,p,v);
    else update(root*2+1,mid+1,r,p,v);
    push_up(root);
}
int q_sum(int root,int l,int r,int ql,int qr) {
    if(ql>r||qr<l)return 0;
    if(ql<=l&&r<=qr)return sum[root];
    int mid=(l+r)/2;
    return q_sum(root*2,l,mid,ql,qr)+q_sum(root*2+1,mid+1,r,ql,qr);
}
int main() {
    int n,i,j,m=32000;
    int _hash[20000];
    scanf("%d",&n);
    memset(_hash,0,sizeof(_hash));
    for(i=0; i<n; i++) {
        scanf("%d%d",&p[i].x,&p[i].y);
        _hash[q_sum(1,0,m,0,p[i].x)]++;
        update(1,0,m,p[i].x,1);
    }
    for(i=0; i<n; i++)
        printf("%d\n",_hash[i]);
    return 0;
}

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

Output

Sample Input

5
1 1
5 1
7 1
3 3
5 5

Sample Output

1
2
1
1
0

Hint

POJ2352_Stars(线段树/单点更新),布布扣,bubuko.com

POJ2352_Stars(线段树/单点更新)

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原文地址：http://blog.csdn.net/juncoder/article/details/38459191