【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。

  1 /* 3234 */
  2 #include <iostream>
  3 #include <string>
  4 #include <map>
  5 #include <queue>
  6 #include <set>
  7 #include <stack>
  8 #include <vector>
  9 #include <deque>
 10 #include <algorithm>
 11 #include <cstdio>
 12 #include <cmath>
 13 #include <ctime>
 14 #include <cstring>
 15 #include <climits>
 16 #include <cctype>
 17 #include <cassert>
 18 #include <functional>
 19 #include <iterator>
 20 #include <iomanip>
 21 using namespace std;
 22 //#pragma comment(linker,"/STACK:102400000,1024000")
 23
 24 #define sti                set<int>
 25 #define stpii            set<pair<int, int> >
 26 #define mpii            map<int,int>
 27 #define vi                vector<int>
 28 #define pii                pair<int,int>
 29 #define vpii            vector<pair<int,int> >
 30 #define rep(i, a, n)     for (int i=a;i<n;++i)
 31 #define per(i, a, n)     for (int i=n-1;i>=a;--i)
 32 #define clr                clear
 33 #define pb                 push_back
 34 #define mp                 make_pair
 35 #define fir                first
 36 #define sec                second
 37 #define all(x)             (x).begin(),(x).end()
 38 #define SZ(x)             ((int)(x).size())
 39 #define lson            l, mid, rt<<1
 40 #define rson            mid+1, r, rt<<1|1
 41
 42 const int maxn = 2e4+5;
 43 const int maxk = 20;
 44 int fa[maxn], val[maxn];
 45 int P[maxk], K;
 46 bool visit[maxk];
 47 int n;
 48
 49 int find(int x) {
 50     if (fa[x] == x)
 51         return x;
 52     int tmp = fa[x];
 53     fa[x] = find(fa[x]);
 54     val[x] ^= val[tmp];
 55     return fa[x];
 56 }
 57
 58 void init() {
 59     rep(i, 0, n+1) {
 60         val[i] = 0;
 61         fa[i] = i;
 62     }
 63 }
 64
 65 bool merge(int u, int v, int x) {
 66     int fu = find(u);
 67     int fv = find(v);
 68
 69     if (fu == fv) {
 70         return (val[u]^val[v]) == x;
 71     }
 72
 73     if (fu == n)    swap(fu, fv);
 74     fa[fu] = fv;
 75     val[fu] = val[u]^val[v]^x;
 76     return true;
 77 }
 78
 79 int Query() {
 80     int f, c;
 81     int ret = 0;
 82
 83     memset(visit, false, sizeof(visit));
 84     rep(i, 0, K)
 85         find(P[i]);
 86     rep(i, 0, K) {
 87         if (visit[i])
 88             continue;
 89         f = fa[P[i]];
 90         c = 0;
 91         rep(j, i, K) {
 92             if (!visit[j] && fa[P[j]]==f) {
 93                 ++c;
 94                 visit[j] = true;
 95                 ret ^= val[P[j]];
 96             }
 97         }
 98         if (f!=n && (c&1))
 99             return -1;
100     }
101
102     return ret;
103 }
104
105 int main() {
106     ios::sync_with_stdio(false);
107     #ifndef ONLINE_JUDGE
108         freopen("data.in", "r", stdin);
109         freopen("data.out", "w", stdout);
110     #endif
111
112     int q;
113     int isn;
114     int a[5], c;
115     int u, v, x;
116     int ans;
117     char cmd[3], line[105];
118     bool flag;
119     int t = 0;
120
121     while (scanf("%d %d", &n, &q)!=EOF && (n||q)) {
122         printf("Case %d:\n", ++t);
123         init();
124         flag = true;
125         isn = 0;
126         while (q--) {
127             scanf("%s%*c", cmd);
128             if (cmd[0] == ‘I‘) {
129                 gets(line);
130             } else {
131                 scanf("%d", &K);
132                 rep(i, 0, K)
133                     scanf("%d", &P[i]);
134             }
135             if (!flag)
136                 continue;
137
138             if (cmd[0] == ‘I‘) {
139                 int len = strlen(line);
140
141                 ++isn;
142                 c = 0;
143                 a[c] = 0;
144                 rep(i, 0, len) {
145                     if (line[i] == ‘ ‘) {
146                         ++c;
147                         a[c] = 0;
148                     } else {
149                         a[c] = 10*a[c] + line[i]-‘0‘;
150                     }
151                 }
152
153                 if (c == 1) {
154                     u = a[0];
155                     v = n;
156                     x = a[1];
157                 } else {
158                     u = a[0];
159                     v = a[1];
160                     x = a[2];
161                 }
162
163                 flag = merge(u, v, x);
164
165                 if (!flag) {
166                     printf("The first %d facts are conflicting.\n", isn);
167                 }
168             } else {
169                 ans = Query();
170                 if (ans == -1) {
171                     puts("I don‘t know.");
172                 } else {
173                     printf("%d\n", ans);
174                 }
175             }
176         }
177
178         putchar(‘\n‘);
179     }
180
181     #ifndef ONLINE_JUDGE
182         printf("time = %d.\n", (int)clock());
183     #endif
184
185     return 0;
186 }