[HDOJ5883]The Best Path（欧拉回路，异或）

 1 #include <bits/stdc++.h>
 2 using namespace std;
 3 #define fr first
 4 #define sc second
 5 #define cl clear
 6 #define BUG puts("here!!!")
 7 #define W(a) while(a--)
 8 #define pb(a) push_back(a)
 9 #define Rint(a) scanf("%d", &a)
10 #define Rll(a) scanf("%I64d", &a)
11 #define Rs(a) scanf("%s", a)
12 #define Cin(a) cin >> a
13 #define FRead() freopen("in", "r", stdin)
14 #define FWrite() freopen("out", "w", stdout)
15 #define Rep(i, len) for(int i = 0; i < (len); i++)
16 #define For(i, a, len) for(int i = (a); i < (len); i++)
17 #define Cls(a) memset((a), 0, sizeof(a))
18 #define Clr(a, x) memset((a), (x), sizeof(a))
19 #define Full(a) memset((a), 0x7f7f7f, sizeof(a))
20 #define lrt rt << 1
21 #define rrt rt << 1 | 1
22 #define pi 3.14159265359
23 #define RT return
24 #define lowbit(x) x & (-x)
25 #define onecnt(x) __builtin_popcount(x)
26 typedef long long LL;
27 typedef long double LD;
28 typedef unsigned long long ULL;
29 typedef pair<int, int> pii;
30 typedef pair<string, int> psi;
31 typedef pair<LL, LL> pll;
32 typedef map<string, int> msi;
33 typedef vector<int> vi;
34 typedef vector<LL> vl;
35 typedef vector<vl> vvl;
36 typedef vector<bool> vb;
37 
38 const int maxn = 100100;
39 int n, m;
40 int ret, tmp;
41 int a[maxn], in[maxn];
42 int pre[maxn];
43 
44 int find(int x) {
45     return x == pre[x] ? x : pre[x] = find(pre[x]);
46 }
47 
48 void unite(int x, int y) {
49     x = find(x);
50     y = find(y);
51     if(x != y) pre[x] = y;
52 }
53 
54 signed main() {
55     // FRead();
56     int T, u, v;
57     Rint(T);
58     W(T) {
59         Cls(in); ret = 0;
60         Rint(n); Rint(m);
61         For(i, 1, n+1) {
62             pre[i] = i;
63             Rint(a[i]);
64         }
65         Rep(i, m) {
66             Rint(u); Rint(v);
67             in[u]++; in[v]++;
68             unite(u, v);
69         }
70         int flag = 0;
71         For(i, 1, n+1) if(in[i] & 1) flag++;
72         if(flag > 2 || flag == 1) {
73             puts("Impossible");
74             continue;
75         }
76         For(i, 1, n+1) {
77             tmp = (in[i] + 1) / 2;
78             W(tmp) ret ^= a[i];
79         }
80         if(flag == 2) {
81             printf("%d\n", ret);
82             continue;
83         }
84         tmp = 0;
85         For(i, 1, n+1) {
86             if(in[i] != 0) {
87                 int cur = ret ^ a[i];
88                 tmp = max(tmp, cur);
89             }
90         }
91         printf("%d\n", tmp);
92     }
93     RT 0;
94 }