[POJ2352] Stars（树状数组）

传送门

先按照下标x排序，然后依次把y加入树状数组，边加入边统计即可。

注意下标re从零开始，需+1s

——代码

 # include <iostream>
 # include <cstdio>
 # include <cstring>
 # include <string>
 # include <cmath>
 # include <vector>
 # include <map>
 # include <queue>
 # include <cstdlib>
 # include <algorithm>
 # define MAXN
 using namespace std;

 inline int get_num() {
     int k = , f = ;
     char c = getchar();
     for(; !isdigit(c); c = getchar()) if(c == '-') f = -;
     for(; isdigit(c); c = getchar()) k = k *  + c - '';
     return k * f;
 }

 int n;
 int c[MAXN], ans[MAXN];
 struct node
 {
     int a, b;
 }p[MAXN];

 inline bool cmp(node x, node y)
 {
     return x.a < y.a || (x.a == y.a && x.b < y.b);
 }

 inline int lowbit(int x)
 {
     return x & -x;
 }

 inline int query(int x)
 {
     int ans = ;
     for(; x; x -= lowbit(x)) ans += c[x];
     return ans;
 }

 inline void add(int x)
 {
     for(; x <= ; x += lowbit(x)) c[x] += ;
 }

 int main()
 {
     int i, t;
     n = get_num();
     for(i = ; i <= n; i++)
     {
         p[i].a = get_num() + ;
         p[i].b = get_num() + ;
     }
     sort(p + , p + n + , cmp);
     for(i = ; i <= n; i++)
     {
         t = query(p[i].b);
         add(p[i].b);
         ans[t]++;
     }
     for(i = ; i < n; i++) printf("%d\n", ans[i]);
     return ;
 }