HDU 1217 Arbitrage

It means N currencies and M exchange rates between currencies,
Let you determine whether a currency exists after several currency exchanges
The value is greater than the original value, for example, the dollar: dollar = 1: 1;
Let you determine whether the current currency exchange rate can be used.
Make $: USD> 1: 1; Use the Floyd algorithm. The Code is as follows: 1 # include <iostream>
2 # include <queue>
3 # include <cstring>
4 # define size 40
5 # define inf 0
6 using namespace std;
7 char s1 [100], s2 [100], str [40] [100];
8 double map [size] [size], dir [size], x;
9 int n, m, k, a, B, flag = 1;
10
11 int tree (char s [])
12 {
13 for (int a = 0; a <n; a ++)
14 if (strcmp (s, str [a]) = 0) return;
15}
16
17 int main ()
18 {
19 while (scanf ("% d", & n), n)
20 {
21 int c, d, e;
22 k = 0;
23 for (a = 0; a <n; a ++)
24 {
25 scanf ("% s", & str [a]);
26}
27 scanf ("% d", & m );
28 for (a = 0; a <size; a ++)
29 for (B = 0; B <size; B ++)
30 map [a] [B] = 0;
31 while (m --)
32 {
33 scanf ("% s % lf % s", & s1, & x, & s2 );
34 a = tree (s1 );
35 B = tree (s2 );
36 map [a] [B] = x;
37}
38 for (c = 0; c <n; c ++)
39 for (d = 0; d <n; d ++)
40 for (e = 0; e <n; e ++)
41 if (map [d] [c] * map [c] [e]> map [d] [e])
42 {
43 map [d] [e] = map [d] [c] * map [c] [e];
44 if (map [0] [0]> 1) break;
45}
46 if (map [0] [0]> 1)
47 cout <"Case" <flag <": Yes" <endl;
48 else
49 cout <"Case" <flag <": No" <endl;
50 flag ++;
51}
52}