【HDOJ】3234 Exclusive-OR

并查集。对于对元素赋值操作，更改为I p n v。令val[n]=0（任何数与0异或仍为原值）。
考虑fa[x] = fx, fa[y] = fy。
如果使得fa[fx] = fy, 那么val[fx] = TrueVal[fx] ^ TrueVal[fy] = (val[x] ^ TrueVal[x]) ^ (val[y] ^ TrueVal[y]) = (val[x] ^ val[y]) ^ (TrueVal[x] ^ TrueVal[y]) = val[x] ^ val[y] ^ z。
同时每次find时，也需要更新val(因为fa不同了)。
对于Query操作，有效的Query为cnt为偶数或者root为n。
输出样例有问题，每个case后有空行。

 /* 3234 */
 #include <iostream>
 #include <string>
 #include <map>
 #include <queue>
 #include <set>
 #include <stack>
 #include <vector>
 #include <deque>
 #include <algorithm>
 #include <cstdio>
 #include <cmath>
 #include <ctime>
 #include <cstring>
 #include <climits>
 #include <cctype>
 #include <cassert>
 #include <functional>
 #include <iterator>
 #include <iomanip>
 using namespace std;
 //#pragma comment(linker,"/STACK:102400000,1024000")

 #define sti                set<int>
 #define stpii            set<pair<int, int> >
 #define mpii            map<int,int>
 #define vi                vector<int>
 #define pii                pair<int,int>
 #define vpii            vector<pair<int,int> >
 #define rep(i, a, n)     for (int i=a;i<n;++i)
 #define per(i, a, n)     for (int i=n-1;i>=a;--i)
 #define clr                clear
 #define pb                 push_back
 #define mp                 make_pair
 #define fir                first
 #define sec                second
 #define all(x)             (x).begin(),(x).end()
 #define SZ(x)             ((int)(x).size())
 #define lson            l, mid, rt<<1
 #define rson            mid+1, r, rt<<1|1

 const int maxn = 2e4+;
 const int maxk = ;
 int fa[maxn], val[maxn];
 int P[maxk], K;
 bool visit[maxk];
 int n;

 int find(int x) {
     if (fa[x] == x)
         return x;
     int tmp = fa[x];
     fa[x] = find(fa[x]);
     val[x] ^= val[tmp];
     return fa[x];
 }

 void init() {
     rep(i, , n+) {
         val[i] = ;
         fa[i] = i;
     }
 }

 bool merge(int u, int v, int x) {
     int fu = find(u);
     int fv = find(v);

     if (fu == fv) {
         return (val[u]^val[v]) == x;
     }

     if (fu == n)    swap(fu, fv);
     fa[fu] = fv;
     val[fu] = val[u]^val[v]^x;
     return true;
 }

 int Query() {
     int f, c;
     int ret = ;

     memset(visit, false, sizeof(visit));
     rep(i, , K)
         find(P[i]);
     rep(i, , K) {
         if (visit[i])
             continue;
         f = fa[P[i]];
         c = ;
         rep(j, i, K) {
             if (!visit[j] && fa[P[j]]==f) {
                 ++c;
                 visit[j] = true;
                 ret ^= val[P[j]];
             }
         }
         if (f!=n && (c&))
             return -;
     }

     return ret;
 }

 int main() {
     ios::sync_with_stdio(false);
     #ifndef ONLINE_JUDGE
         freopen("data.in", "r", stdin);
         freopen("data.out", "w", stdout);
     #endif

     int q;
     int isn;
     int a[], c;
     int u, v, x;
     int ans;
     char cmd[], line[];
     bool flag;
     int t = ;

     while (scanf("%d %d", &n, &q)!=EOF && (n||q)) {
         printf("Case %d:\n", ++t);
         init();
         flag = true;
         isn = ;
         while (q--) {
             scanf("%s%*c", cmd);
             if (cmd[] == 'I') {
                 gets(line);
             } else {
                 scanf("%d", &K);
                 rep(i, , K)
                     scanf("%d", &P[i]);
             }
             if (!flag)
                 continue;

             if (cmd[] == 'I') {
                 int len = strlen(line);

                 ++isn;
                 c = ;
                 a[c] = ;
                 rep(i, , len) {
                     if (line[i] == ' ') {
                         ++c;
                         a[c] = ;
                     } else {
                         a[c] = *a[c] + line[i]-'';
                     }
                 }

                 if (c == ) {
                     u = a[];
                     v = n;
                     x = a[];
                 } else {
                     u = a[];
                     v = a[];
                     x = a[];
                 }

                 flag = merge(u, v, x);

                 if (!flag) {
                     printf("The first %d facts are conflicting.\n", isn);
                 }
             } else {
                 ans = Query();
                 if (ans == -) {
                     puts("I don't know.");
                 } else {
                     printf("%d\n", ans);
                 }
             }
         }

         putchar('\n');
     }

     #ifndef ONLINE_JUDGE
         printf("time = %d.\n", (int)clock());
     #endif

     return ;
 }