POJ2352 Stars

试了一把树状数组，代码果然很简单。

#include <iostream>
#include <string>
#include <vector>
#include <stack>
#include <sstream>
#include <utility>
using namespace std;

vector<int> cnt;
vector<int> arr; // effective index: 1..N

int lowb(int t) {
  return t & (-t);
}

void add(int i, int x) {
  int size = arr.size();
  for (; i < size; i += lowb(i)) {
    arr[i] += x;
  }
}

int sum(int i) {
  int s = 0;
  for (; i > 0; i -= lowb(i)) {
    s += arr[i];
  }
  return s;
}

int main() {
  int n = 0;
  while (scanf("%d",&n) != EOF) {
    cnt.assign(15010, 0);
    arr.assign(32010, 0);
    for (int i = 0; i < n; i++) {
      int x, y;
      scanf("%d%d",&x, &y);
      int tmp = sum(x + 1);
      cnt[tmp]++;
      add(x + 1, 1);
    }
    for(int i = 0; i < n; i++) {
      printf("%d
",cnt[i]);
    }
  } 
  return 0;
}