hdu5883(欧拉路)

 1 #include<cstring>
 2 #include<algorithm>
 3 #include<queue>
 4 #include<vector>
 5 #include<set>
 6 #define CLR(a,b) memset((a),(b),sizeof((a)))
 7 using namespace std;
 8 
 9 const int N = 100003;
10 const int inf = 0x3f3f3f3f;
11 int n, m;
12 int a[N];
13 int du[N];
14 
15 int main(){
16     int t, i, j, b, c, f, ans, dd, ma;
17     scanf("%d", &t);
18     while(t--){
19         ans = 0;
20         scanf("%d %d", &n, &m);
21         f = 0;
22         ma = 0;
23         CLR(du, 0);
24         for(i = 1; i<= n; ++i)
25             scanf("%d", &a[i]);
26         for(i = 1; i <= m; ++i){
27             scanf("%d %d", &b, &c);
28             du[b]++; du[c]++;
29         }
30         dd = 0;
31         for(i = 1; i <= n; ++i){
32             if(du[i]%2) dd++;
33         }
34         if(dd == 2 || dd==0) f = 1; // 欧拉路的奇度顶点数为 2 或 0
35         if(!f){printf("Impossible\n");continue;}
36         for(i = 1; i<= n; ++i){
37             if(((du[i] + 1)/2) %2 == 1)
38                 ans ^= a[i];
39         }
40         if(!dd){//欧拉回路时枚举起点
41             for(i = 1; i <= n; ++i){
42                 int t = ans ^a[i];
43                 ma= max(ma, t);
44             }
45             ans = ma;
46         }
47         printf("%d\n", ans);
48     }
49     return 0;
50 }