[HDOJ6147] Pokemon GO II（规律，几何）

题目链接：http://acm.hdu.edu.cn/showproblem.php?pid=6147

果然是原题之星…原题链接：http://contest.felk.cvut.cz/14prg/solved/self/

确实很容易发现，第一次覆盖一定是与轨迹上的前8段（或者更 少）中的某一段。

 1 /*
 2  * CTU Open Contest 2014
 3  * Problem solution: Self Intersection
 4  *
 5  * Author: Michal "Mimino" Danilak
 6  */
 7 
 8 #include <cstdio>
 9 #include <algorithm>
10 using namespace std;
11  
12 const int MAX = 1000007, dx[] = { 0, 1, 0, -1 }, dy[] = { 1, 0, -1, 0 };
13 int N, a[MAX];
14  
15 struct Point
16 {
17     int x, y;
18     Point(int _x = 0, int _y = 0) :
19         x(_x), y(_y) {}
20 } points[MAX];
21  
22 // true, if intervals [a,b] and [c,d] have non-empty intersection
23 bool overlap(int a, int b, int c, int d)
24 {
25     if (a > b) swap(a, b);
26     if (c > d) swap(c, d);
27     return !(b < c || d < a);
28 }
29  
30 // true if line segments [a1,a2] and [b1,b2] have non-empty intersection
31 bool intersect(Point a1, Point a2, Point b1, Point b2)
32 {
33     bool is_vertical_a = (a1.x == a2.x), is_vertical_b = (b1.x == b2.x);
34     if (is_vertical_a && is_vertical_b)
35         return a1.x == b1.x && overlap(a1.y, a2.y, b1.y, b2.y);
36     if (!is_vertical_a && !is_vertical_b)
37         return a1.y == b1.y && overlap(a1.x, a2.x, b1.x, b2.x);
38     // make a horizontal and b vertical
39     if (is_vertical_a)
40     {
41         swap(a1, b1);
42         swap(a2, b2);
43     }
44     return !(
45         max(a1.x, a2.x) < b1.x ||
46         min(a1.x, a2.x) > b1.x ||
47         max(b1.y, b2.y) < a1.y ||
48         min(b1.y, b2.y) > a1.y);
49 }
50  
51 int solve()
52 {
53     int x = 0, y = 0;
54     for (int i = 0; i < N; ++i)
55     {
56         x += dx[i & 3] * a[i];
57         y += dy[i & 3] * a[i];
58         points[i + 1].x = x;
59         points[i + 1].y = y;
60         for (int j = max(0, i - 8); j < i - 2; ++j)
61         if (intersect(points[j], points[j + 1], points[i], points[i + 1]))
62             return i;
63     }
64     return -1;
65 }
66  
67 int main()
68 {
69     int T;
70     scanf("%d", &T);
71     while(T--) {
72         scanf("%d", &N);
73         for (int i = 0; i < N; ++i)
74             scanf("%d", a + i);
75         int result = solve();
76         if (result == -1)
77             printf("Catch you\n");
78         else
79             printf("%d\n", result+1);
80     }
81  
82     return 0;
83 }

 

posted @ 2017-08-19 11:18  Kirai  阅读(341)  评论(0)  编辑  收藏  举报