HDU 3234 Exclusive-OR and check set deformation

/* From: http://www.cppblog.com/Yuan/archive/2010/09/02/125667.html? Opt = admin slightly rewrite there are n (n <= 20000) unknown integer X0, X1, X2Xn-1, there are the following Q (Q <= 40000) Operations: I p v: tell you Xp = v I p q v: Tell you Xp Xor Xq = v Q k p1 p2... Pk: Ask Xp1 Xor Xp2 .. Xor Xpk, k is not greater than 15. If the current I conflicts with the previous one, jump out and check the set extension! For I p v, if a point Xn = 0 is set, it can be regarded as I p n v (different from 0 or). So for all those I, it is a ^ B = v, for the effect of the two, val [I] = Xi ^ Xfa [I] is the same as the above. fa [I] is the father of I: 1) I p q v First find if p q is in the same set, and judge whether there is Xp ^ Xq = v is not a conflict. Otherwise, the merged points should always be kept as the root. 2) Q k p1pk Xp1 ^ Xp2 ^ Xpk is converted: val [p1] ^ val [p2] ^ val [k] ^ (Xfa [p1] ^ Xfa [p2] ^ Xfa [pk]) val [pi] known, you only need to determine whether Xfa [pi] is known because it is an exclusive or an odd number of Xfa [pi. Determine whether the root is Xn */# include <cstdio> # include <cstring> # include <algorithm> # include <vector> using namespace std; const int MAXN = 20010; int fa [MAXN], val [MAXN]; int n, q; void init (int n) {for (int I = 0; I <= n; I ++) {val [I] = 0; fa [I] = I ;}} int find (int a) {if (! = Fa [a]) {int t = fa [a]; fa [a] = find (fa [a]); val [a] ^ = val [t];} return fa [a];} bool unin (int a, int B, int v) {int ra = find (a); int rb = find (B ); if (ra = rb) {return v = (val [a] ^ val [B]);} if (ra = n) swap (ra, rb ); fa [ra] = rb; val [ra] = val [a] ^ val [B] ^ v; return true;} char cmd [MAXN]; int main () {// freopen ("in", "r", stdin); int t = 1; while (scanf ("% d", & n, & q ), n) {printf ("Case % d: \ n", t ++); init (n); int fact = 0; bool err = False; for (int I = 0; I <q; I ++) {scanf ("% c", & cmd [0]); if (err) {gets (cmd); continue;} if (cmd [0] = 'I') {gets (cmd); // fact ++; int x, y, v; if (sscanf (cmd, "% d", & x, & y, & v) = 2) // sscanf () directly scanf () I am not sure why {swap (y, v); y = n;} if (! Unin (x, y, v) {err = true; printf ("The first % d facts are conflicting. \ n ", fact) ;}} else {int k, x, ans = 0, pos =-1, flag = true; vector <pair <int, int> V; scanf ("% d", & k); for (int I = 0, jj; I <k; I ++) {scanf ("% d", & x ); int rx = find (x); ans ^ = val [x]; for (jj = 0; jj <V. size (); jj ++) {if (V [jj]. first = rx) break;} if (jj = V. size () V. push_back (make_pair (rx, 1); else V [jj]. second ++;} for (int j = 0; j <V. size (); j ++) {if (V [j]. secon D & 1) {if (V [j]. first! = N) {flag = false; break ;}} if (flag) printf ("% d \ n", ans); else puts ("I don't know. ") ;}} puts (" ");} return 0 ;}