Poj big Christmas tree (Basic Shortest Path)

Big Christmas tree

Question Analysis:

You are advised to construct a Christmas tree so that (sum of weights of all descendant nodes) × (unit price of the edge) is as small as possible. After conversion, the distance between the root node and each node is the shortest, that is, the shortest path. The spanning tree may time out. I have not tried it. Then, the optimization solution should be used to solve the shortest circuit. Otherwise, it will time out. The final answer is: Sum = W [1] * Dist [1] + W [2] * Dist [2] + ..... W [N] * Dist [N]. you can simply push the sample by yourself.

It is a simple and short circuit. The result is that it is a waste of time in the morning because it is not cleared .,,, T_t

Remember Later !!! Blood lessons !!!!!

# Include <iostream> # include <algorithm> # include <vector> # include <queue> # include <cstdio> # include <cstring> using namespace STD; typedef long ll; const int maxn = 50000 + 100; struct edge {int from, to; ll C; edge () {}; edge (INT _ F, int _ T, ll _ C ): from (_ F), to (_ T), C (_ C) {};}; vector <edge> edges; vector <int> G [maxn]; ll weight [maxn], DIST [maxn]; bool VST [maxn]; int numv, nume; // clear void Init () {edges. clear (); fo R (INT I = 0; I <= numv; ++ I) {G [I]. clear () ;}} void addedge (int x, int y, ll c) {edges. push_back (edge (X, Y, C); int SZ = edges. size (); G [X]. push_back (SZ-1);} // relaxation operation bool relax (int u, int V, ll c) {If (Dist [u] =-1) | (Dist [u]> Dist [v] + C) {Dist [u] = DIST [v] + C; return true;} return false ;} // solve the shortest void spfa (ll src) {int I, U, K; queue <int> q; for (I = 0; I <= numv; ++ I) {VST [I] = 0; Dist [I] =-1;} Q. push (SRC); Dist [SRC] = 0; while (! Q. empty () {u = Q. front (); q. pop (); VST [u] = 0; for (I = 0; I <(INT) g [u]. size (); ++ I) {k = G [u] [I]; edge & E = edges [k]; If (relax (E. to, U, E. c )&&! VST [E. to]) {VST [E. to] = 1; q. push (E. to) ;}}} int main () {int t; scanf ("% d", & T); While (t --) {int X, Y; ll C; scanf ("% d", & numv, & nume); Init (); For (INT I = 1; I <= numv; ++ I) {CIN> weight [I] ;}for (INT I = 0; I <nume; ++ I) {scanf ("% d % i64d", & X, & Y, & C); addedge (X, Y, c); addedge (Y, X, c);} spfa (1); LL sum = 0; bool flag = false; For (INT I = 1; I <= numv; ++ I) {If (Dist [I] =-1) {flag = true; break;} sum + = DIST [I] * weight [I];} If (FLAG) puts ("No answer"); else printf ("% i64d \ n ", sum);} return 0 ;}

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Poj big Christmas tree (Basic Shortest Path)