# 赶牛入圈

 1 #include <bits/stdc++.h>
2 using namespace std;
3 typedef pair<int, int> PII;
4 const int N = 1010; //最多给了500个草的位置，所以最多有1000个数需要离散化
5 int C, n;
6 PII points[N]; //存储草的位置
7 int sum[N][N]; //前缀和数组
8 vector<int> numbers; //存储所有离散化之后的数
9 bool check(int len) {
10     for (int x1 = 1, x2 = 1; x2 < numbers.size(); x2++) {
11         while (numbers[x2] - numbers[x1] + 1 > len) {
12             x1++;
13         }
14         for (int y1 = 1, y2 = 1; y2 < numbers.size(); y2++) {
15             while (numbers[y2] - numbers[y1] + 1 > len) {
16                 y1++;
17             }
18             if (sum[x2][y2] - sum[x1 - 1][y2] - sum[x2][y1 - 1] + sum[x1 - 1][y1 - 1] >= C) {
19                 return true;
20             }
21         }
22     }
23     return false;
24 }
25 int get(int x) {
26     int l = 0, r = numbers.size() - 1;
27     while (l < r) {
28         int mid = (l + r) / 2;
29         if (numbers[mid] >= x) {
30             r = mid;
31         } else {
32             l = mid + 1;
33         }
34     }
35     return l;
36 }
37 int main() {
38     cin >> C >> n;
39     numbers.push_back(0);
40     for (int i = 0; i < n; i++) {
41         int x, y;
42         cin >> x >> y;
43         numbers.push_back(x);
44         numbers.push_back(y);
45         points[i] = {x, y};
46     }
47     sort(numbers.begin(), numbers.end());
48     numbers.erase(unique(numbers.begin(), numbers.end()), numbers.end());
49     for (int i = 0; i < n; i++) {
50         int x = get(points[i].first), y = get(points[i].second);
51         sum[x][y]++;
52     }
53     for (int i = 1; i < numbers.size(); i++) { //计算前缀和
54         for (int j = 1; j < numbers.size(); j++) {
55             sum[i][j] += sum[i - 1][j] + sum[i][j - 1] - sum[i - 1][j - 1];
56         }
57     }
58     int l = 1, r = 10000; //二分
59     while (l < r) {
60         int mid = (l + r) / 2;
61         if (check(mid)) {
62             r = mid;
63         } else {
64             l = mid + 1;
65         }
66     }
67     cout << l << endl;
68     return 0;
69 }

posted @ 2020-11-24 11:12  kyk333  阅读(84)  评论(0编辑  收藏  举报