[Rmq + LCA] poj 1986

The data of OJ May be faulty. It seems that the connectivity and disconnectivity are always possible. To be conservative, use the query set to determine whether the connection is successful. Add the virtual root to form a tree and use the offline rmq.

# Define n 40010 struct edge {int V; int Len; int next;} e [2 * n]; int ecnt; int head [N]; bool vis [N]; int N; // point int R [N]; // the first occurrence of the I point subscript int P [N * 2]; // record path point number int dis [N]; // distance from the root int Dep [2 * n]; // depth int DP [20] [2 * n]; // The closest common ancestor subscript of the 2 ^ I path starting from J. Here !!! The second dimension must be 2 times the size !! Int num; int Fa [N]; void Init () {memset (Head,-1, sizeof (head); memset (R,-1, sizeof (R )); memset (VIS, 0, sizeof (VIS); For (INT I = 1; I <= N; I ++) Fa [I] = I; ecnt = 0 ;} void add (int u, int V, int Len) {e [ecnt]. V = V; E [ecnt]. len = Len; E [ecnt]. next = head [u]; head [u] = ecnt ++; E [ecnt]. V = u; E [ecnt]. len = Len; E [ecnt]. next = head [v]; head [v] = ecnt ++;} int find (int x) {If (Fa [x]! = X) Fa [x] = find (Fa [x]); Return Fa [X];} void uni (int u, int V) {int A = find (U); int B = find (V); if (a = B) return; Fa [a] = B;} void DFS (INT U, int depth) {vis [u] = 1; p [++ num] = u; Dep [num] = depth; For (INT I = head [u]; I! =-1; I = E [I]. Next) {int v = E [I]. V; If (! Vis [v]) {dis [v] = dis [u] + E [I]. len; DFS (v, depth + 1); P [++ num] = u; Dep [num] = depth ;}} void init_rmq () {int I, J; for (I = 1; I <= num; I ++) {If (R [p [I] =-1) {R [p [I] = I ;}} for (I = 1; I <= num; I ++) {DP [0] [I] = I ;} int t = (INT) (log (Num * 1.0)/log (2.0); for (I = 1; I <= T; I ++) {for (j = 1; j + (1 <(I-1) <= num; j ++) {int A = DP [I-1] [J], B = DP [I-1] [J + (1 <(I-1)]; If (DEP [a] <= Dep [B]) {DP [I] [J] = A;} else DP [I] [J] = B ;}}} Int rmq (int u, int v) {// returns the number of the nearest common ancestor, if (R [u]> = R [v]) Swap (u, v ); int S = R [u], t = R [v]; int K = (INT) (log (t-s + 1) * 1.0) /log (2.0); int A = DP [k] [s], B = DP [k] [T-(1 <k) + 1]; if (DEP [a] <= Dep [B]) return P [a]; else return P [B];} int main () {int M, C; while (scanf ("% d", & N, & M )! =-1) {int I, j; Init (); int x, y, z; char STR [3]; while (M --) {scanf ("% d % s", & X, & Y, & Z, STR); add (x, y, z); UNI (X, y);} for (I = 1; I <= N; I ++) {If (Fa [I] = I) {Add (I, 0, 0 ); // Add virtual root 0 to change forest to tree} num = 0; DIS [0] = Dep [0] = 0; DFS (); init_rmq (); scanf ("% d", & C); While (c --) {scanf ("% d", & X, & Y); int F = rmq (X, y); If (! F) puts ("0"); else printf ("% d \ n", DIS [x] + dis [y]-2 * Dis [f]);} return 0 ;}