HDU 2352 Stars

 1 #include <cstdio>
 2 #include <cstring>
 3 #define lowbit(x) (x)&(-x)
 4 
 5 int c[32005];   //树状数组
 6 int ans[15005]; //存储结果
 7 
 8 void add(int i, int val)
 9 {
10     while(i <= 32001){  //注意为32001，而不是32000
11         c[i] += val;
12         i += lowbit(i);
13     }
14 }
15 
16 int sum(int i)
17 {
18     int ret = 0;
19     while(i > 0){
20         ret += c[i];
21         i -= lowbit(i);
22     }
23     return ret;
24 }
25 
26 int main()
27 {
28     int n;
29     scanf("%d", &n);
30     int x, y;
31     //先将两个数组清零
32     memset(c, 0, sizeof(c));
33     memset(ans, 0, sizeof(ans));
34     for(int i = 1; i <= n; ++i){
35         scanf("%d%d", &x, &y);
36         ++x;    //索引加1
37         ++ans[sum(x)];  //ans[]的对应处加上1
38         add(x, 1);  //增加一个横坐标为x的点
39     }
40     for(int i = 0; i < n; ++i)
41         printf("%d\n", ans[i]);
42     return 0;
43 }