課件中有一個討論：有沒有必要用到鄰接矩陣或鄰接表來存儲圖？讓我在迷茫中想到用一個一維數組來解決問題或許不錯，我就這樣做了。有一個小點，為了不出現浮點數，我在計算時把中心小島的半徑放大了10倍
1 #include <stdio.h>
2 #include <stdlib.h>
3 #include <stdbool.h>
4
5 const int L = 50, R = 75;
6
7 bool DFS(int * a, int i, int N, int D);
8 bool firstJump(int * a, int i, int D);
9 bool isSafe(int * a, int i, int D);
10 bool jump(int * a, int i, int j, int D);
11
12 int main()
13 {
14 // freopen("in.txt", "r", stdin);
15 int i, N, D;
16 scanf("%d%d", &N, &D);
17 int a[3 * N];
18 for(i = 0; i < N; i++)
19 {
20 scanf("%d%d", &a[3 * i], &a[3 * i + 1]);
21 a[3 * i + 2] = 0;
22 }
23
24 bool answer = false;
25 for(i = 0; i < N; i++)
26 {
27 if(a[3 * i + 2] == 0 && firstJump(a, i, D))
28 {
29 answer = DFS(a, i, N, D);
30 if(answer)
31 break;
32 }
33 }
34
35 if(answer)
36 printf("Yes\n");
37 else
38 printf("No\n");
39 // fclose(stdin);
40 return 0;
41 }
42
43 bool DFS(int * a, int i, int N, int D)
44 {
45 bool answer;
46 int j;
47
48 answer = false;
49 a[3 * i + 2] = 1;
50 if(isSafe(a, i, D))
51 answer = true;
52 else
53 {
54 for(j = 0; j < N; j++)
55 {
56 if(a[3 * j + 2] == 0 && jump(a, i, j, D))
57 {
58 answer = DFS(a, j, N, D);
59 if(answer)
60 break;
61 }
62 }
63 }
64
65 return answer;
66 }
67
68 bool firstJump(int * a, int i, int D)
69 {
70 if(100 * (a[3 * i] * a[3 * i] + a[3 * i + 1] * a[3 * i + 1]) > (10 * D + R) * (10 * D + R))
71 return false;
72 else
73 return true;
74 }
75
76 bool isSafe(int * a, int i, int D)
77 {
78 if(abs(a[3 * i]) < L - D && abs(a[3 * i + 1]) < L - D)
79 return false;
80 else
81 return true;
82 }
83
84 bool jump(int * a, int i, int j, int D)
85 {
86 int x, y;
87 x = a[3 * i] - a[3 * j];
88 x = x > 0 ? x : -x;
89 y = a[3 * i + 1] - a[3 * j + 1];
90 y = y > 0 ? y : -y;
91
92 if(x * x + y * y > D * D)
93 return false;
94 else
95 return true;
96 }
This time let us consider the situation in the movie "Live and Let Die" in which James Bond, the world's most famous spy, was captured by a group of drug dealers. He was sent to a small piece of land at the center of a lake filled with crocodiles. There he performed the most daring action to escape -- he jumped onto the head of the nearest crocodile! Before the animal realized what was happening, James jumped again onto the next big head... Finally he reached the bank before the last crocodile could bite him (actually the stunt man was caught by the big mouth and barely escaped with his extra thick boot).
Assume that the lake is a 100 by 100 square one. Assume that the center of the lake is at (0,0) and the northeast corner at (50,50). The central island is a disk centered at (0,0) with the diameter of 15. A number of crocodiles are in the lake at various positions. Given the coordinates of each crocodile and the distance that James could jump, you must tell him whether or not he can escape.
Input Specification:
Each input file contains one test case. Each case starts with a line containing two positive integers N (<=100), the number of crocodiles, and D, the maximum distance that James could jump. Then N lines follow, each containing the (x, y) location of a crocodile. Note that no two crocodiles are staying at the same position.
Output Specification:
For each test case, print in a line "Yes" if James can escape, or "No" if not.
Sample Input 1:
14 20 25 -15 -25 28 8 49 29 15 -35 -2 5 28 27 -29 -8 -28 -20 -35 -25 -20 -13 29 -30 15 -35 40 12 12
Sample Output 1:
Yes
Sample Input 2:
4 13 -12 12 12 12 -12 -12 12 -12
Sample Output 2:
No
