UVa 1312 - Cricket Field (高效枚举)

题意

找出最大的正方形，不包含点。

思路

先仰慕帆神。

枚举左右边界，然后从下到上枚举上边界，维护最大值和左下角的坐标。

代码

1. int n, vis[MAXN], width;
2. vector x;
3. pii P[MAXN];
5. bool cmp(const pii &a, const pii &b)
6. {
7. return a.Y < b.Y;
8. }
10. void Handle()
11. {
12. for (int i = 0; i < n; i++) scanf("%d%d", &P[i].X, &P[i].Y);
13. x.clear();
14. MS(vis, 0);
15. vis[0] = 1;
16. x.PB(0);
17. for (int i = 0; i < n; i++)
18. {
19. if (!vis[P[i].X])
20. {
21. vis[P[i].X] = 1;
22. x.PB(P[i].X);
23. }
24. }
25. if (!vis[width]) x.PB(width);
26. sort(x.begin(), x.end());
27. }
29. int main()
30. {
31. //ROP;
32. int height, T;
33. scanf("%d", &T);
34. while (T--)
35. {
36. scanf("%d%d%d", &n, &width, &height);
37. Handle();
38. sort(P, P + n, cmp);
39. int maxValue = 0, curBottom;
40. pii ans;
41. for (int i = 0; i < SZ(x); i++)
42. {
43. for (int j = i+1; j < SZ(x); j++)
44. {
45. int tmpWide = x[j] - x[i], curBottom = 0;
46. for (int k = 0; k < n; k++)
47. {
48. if (P[k].X <= x[i] || P[k].X >= x[j]) continue;
49. int tmpHeight = P[k].Y - curBottom;
50. if (maxValue < min(tmpWide, tmpHeight))
51. {
52. maxValue = min(tmpWide, tmpHeight);
53. ans.X = x[i]; ans.Y = curBottom;
54. }
55. curBottom = P[k].Y;
56. }
57. int tmpHeight = height - curBottom;
58. if (maxValue < min(tmpWide, tmpHeight))
59. {
60. maxValue = min(tmpWide, tmpHeight);
61. ans.X = x[i]; ans.Y = curBottom;
62. }
63. }
64. }
65. printf("%d %d %d\n", ans.X, ans.Y, maxValue);
66. if (T) puts("");
67. }
68. return 0;
69. }