[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

 1 # include <iostream>
 2 # include <cstdio>
 3 # include <cstring>
 4 # include <string>
 5 # include <cmath>
 6 # include <vector>
 7 # include <map>
 8 # include <queue>
 9 # include <cstdlib>
10 # include <algorithm>
11 # define MAXN 32002
12 using namespace std;
13
14 inline int get_num() {
15     int k = 0, f = 1;
16     char c = getchar();
17     for(; !isdigit(c); c = getchar()) if(c == ‘-‘) f = -1;
18     for(; isdigit(c); c = getchar()) k = k * 10 + c - ‘0‘;
19     return k * f;
20 }
21
22 int n;
23 int c[MAXN], ans[MAXN];
24 struct node
25 {
26     int a, b;
27 }p[MAXN];
28
29 inline bool cmp(node x, node y)
30 {
31     return x.a < y.a || (x.a == y.a && x.b < y.b);
32 }
33
34 inline int lowbit(int x)
35 {
36     return x & -x;
37 }
38
39 inline int query(int x)
40 {
41     int ans = 0;
42     for(; x; x -= lowbit(x)) ans += c[x];
43     return ans;
44 }
45
46 inline void add(int x)
47 {
48     for(; x <= 32001; x += lowbit(x)) c[x] += 1;
49 }
50
51 int main()
52 {
53     int i, t;
54     n = get_num();
55     for(i = 1; i <= n; i++)
56     {
57         p[i].a = get_num() + 1;
58         p[i].b = get_num() + 1;
59     }
60     sort(p + 1, p + n + 1, cmp);
61     for(i = 1; i <= n; i++)
62     {
63         t = query(p[i].b);
64         add(p[i].b);
65         ans[t]++;
66     }
67     for(i = 0; i < n; i++) printf("%d\n", ans[i]);
68     return 0;
69 }