HDU 5883 F - The Best Path 欧拉通路 & 欧拉回路

#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cmath>
#include <algorithm>
#define IOS ios::sync_with_stdio(false)
using namespace std;
#define inf (0x3f3f3f3f)
typedef long long int LL;

#include <iostream>
#include <sstream>
#include <vector>
#include <set>
#include <map>
#include <queue>
#include <string>
const int maxn = 1e5 + 20;
int a[maxn];
int Degree[maxn];
void init(int n) {
    for (int i = 1; i <= n; ++i) {
        Degree[i] = 0;
    }
}
void work() {
    int n, m;
    scanf("%d%d", &n, &m);
    init(n);
    for (int i = 1; i <= n; ++i) scanf("%d", &a[i]);
    for (int i = 1; i <= m; ++i) {
        int u, v;
        scanf("%d%d", &u, &v);
        Degree[u]++;
        Degree[v]++;
    }
    int root = 0;
    root = 0;
    for (int i = 1; i <= n; ++i) {
        root += Degree[i] & 1;
        if (Degree[i] == 0) {
            printf("Impossible\n");
            return;
        }
    }
    if (!(root == 0 || root == 2)) {
        printf("Impossible\n");
        return;
    }
    int ans = 0;
    int tans = 0;
    for (int i = 1; i <= n; ++i) {
        int tim = Degree[i] / 2 + (Degree[i] & 1);
        tim &= 1;
        tans ^= a[i] * tim;
    }
    if (root == 0) {
        for (int i = 1; i <= n; ++i) {
            int gg = tans ^ a[i];
            ans = max(ans, gg);
        }
    } else {
        ans = tans;
    }
    printf("%d\n", ans);
}

int main() {
#ifdef local
    freopen("data.txt","r",stdin);
#endif
//    printf("%d\n", 1  ^ 3 ^ 4 ^ 5 ^ 6);
    int t;
    scanf("%d", &t);
    while (t--) work();
    return 0;
}