3804 Query on a tree

The question was so painful that I didn't want to write it again.

 

The idea of the question is very simple. Find the maximum edge weight from node 1 to a node x path not greater than Y

 

Offline operations: mutiset stores negative Edge Weight Values. lower_bound can be used to conveniently obtain the maximum value not greater than Y in the set.

The disgusting part of the question is that you cannot use recursive deep search. You can only write non-recursive versions. The first time you write a non-recursive deep search, you have been writing it for a long time, but a is very happy.

 

# Include <cstdio> <br/> # include <set> <br/> # include <vector> <br/> # include <map> <br/> using namespace STD; <br/> # define maxn 100001 <br/> struct node {<br/> int V, W; // v ID of the next node, W edge weight <br/> node () {}< br/> node (int av, int AW): V (AV), w (AW) {}< br/>}; </P> <p> struct quenode {// because it is an offline operation, therefore, this struct is required to record the output sequence <br/> int V; <br/> int bound; <br/> }; <br/> struct dpstype {// struct used in non-recursive Deep Search <br/> int V, CID; <br/> int insw; <B R/>}; <br/> vector <node> adj [maxn]; <br/> Map <int, int> qmp [maxn]; <br/> vector <quenode> qseq; <br/> Multiset <int> MS; <br/> int vis [maxn]; <br/> int t, n, m; </P> <p> dpstype vsta [maxn]; <br/> void solve () {<br/> int DPT = 0; <br/> vsta [DPT]. cid =-1; <br/> vsta [DPT]. V = 1; <br/> vis [vsta [DPT]. v] = 1; <br/> while (DPT! =-1) {<br/> const dpstype cNode = vsta [DPT]; <br/> If (cNode. CID + 1 <adj [cNode. v]. size () {// if this layer does not exceed the boundary, continue the query. <br/> vsta [DPT]. cid = cNode. CID + 1; <br/> int Cu = cNode. v; <br/> int NV = adj [Cu] [vsta [DPT]. CID]. v; <br/> If (! Vis [NV]) {<br/> int insval =-(adj [Cu] [vsta [DPT]. CID]. w); <br/> MS. insert (insval); <br/> ++ DPT; <br/> vsta [DPT]. V = NV; <br/> vsta [DPT]. insw = insval; <br/> vis [NV] = 1; <br/> for (Map <int, int>: iterator iter = qmp [NV]. begin (); iter! = Qmp [NV]. end (); ++ ITER) {<br/> Multiset <int >:: iterator rs = Ms. lower_bound (-(ITER-> first); <br/> If (RS! = Ms. end () {<br/> ITER-> second =-(* RS ); <br/>}< br/>} else {// beyond the boundary, backtracking <br/> vsta [DPT]. cid =-1; <br/> Multiset <int>: iterator EPOS = Ms. find (vsta [DPT]. insw); <br/> If (EPOs! = Ms. end () <br/> MS. erase (EPOs); <br/> -- DPT; <br/>}< br/> void INI (int n) {<br/> MS. clear (); <br/> qseq. clear (); <br/> for (INT I = 0; I <= N; ++ I) {<br/> adj [I]. clear (); <br/> qmp [I]. clear (); <br/> vsta [I]. cid =-1; <br/> vis [I] = 0; <br/>}< br/> int main () {<br/> scanf ("% d", & T); <br/> while (t --) {<br/> scanf ("% d ", & N); <br/> INI (n); <br/> for (INT I = 1; I <= N; ++ I) adj [I]. clear (); <br/> for (INT I = 0; I <n-1; ++ I) {<br/> int U, V, W; <br/> scanf ("% d", & U, & V, & W); <br/> adj [u]. push_back (node (V, W); <br/> adj [v]. push_back (node (u, W); <br/>}< br/> scanf ("% d", & M); <br/> quenode on; <br/> for (INT I = 0; I <m; ++ I) {<br/> int V, B; <br/> scanf ("% d", & V, & B); <br/> On. V = V; <br/> On. bound = B; <br/> qseq. push_back (on); <br/> qmp [v]. insert (pair <int, int> (B,-1); <br/>}< br/> solve (); <br/> for (size_t I = 0; I <qseq. size (); ++ I) {<br/> quenode TMP = qseq [I]; <br/> printf ("% d/N", qmp [TMP. v]. find (TMP. bound)-> second); <br/>}< br/> return 0; <br/>}< br/>