[Codeforces 449B] Jzzhu and Cities

[Topic link]

Https://codeforces.com/contest/449/problem/B

Algorithm

Shortest circuit

Time complexity: O (N ^ 2)

Code

#include <bits/stdc++.h>using namespacestd;Const intMAXN = 1e5 +Ten;Const intINF =2e9;intN, M, K;intMARK[MAXN];Long LongDIST[MAXN];BOOLInq[maxn];vector< pair<int,int> >g[maxn];template<typename t> InlinevoidChkmax (T &x,t y) {x =Max (x, y);} Template<typename t> InlinevoidChkmin (T &x,t y) {x =min (x, y);} Template<typename t> InlinevoidRead (T &x) {T F=1; x =0; Charc =GetChar ();  for(;!isdigit (c); c = GetChar ())if(c = ='-') F =-F;  for(; IsDigit (c); c = GetChar ()) x = (x <<3) + (x <<1) + C-'0'; X*=F;}intMain () {read (n); read (m); Read (k);  for(inti =1; I <= m; i++)        {                intu, V, W; Read (u); Read (v);                Read (w);                G[u].push_back (Make_pair (v,w));        G[v].push_back (Make_pair (u,w)); } Queue<int>Q;  for(inti =1; I <= N; i++) {Dist[i]=INF; Mark[i]=0; Inq[i]=false; } dist[1] =0; Q.push (1); inq[1] =true;  for(inti =1; I <= K; i++)        {                intu, W; Read (u);                Read (w); Mark[u]=1; if(W <Dist[u]) {Dist[u]=W; if(!Inq[u]) {Inq[u]=true;                                Q.push (U); }                        }                }         while(!Q.empty ()) {                intU =Q.front ();                Q.pop (); Inq[u]=false;  for(Unsigned i =0; I < g[u].size (); i++)                {                        intv = g[u][i].first, w =G[u][i].second; if(Dist[u] + w <= dist[v] && mark[v]) mark[v] =0; if(Dist[u] + W <Dist[v]) {Dist[v]= Dist[u] +W; if(!Inq[v]) {Inq[v]=true;                                Q.push (v); }                        }                }        }         for(inti =1; I <= N; i++) K-=Mark[i]; printf ("%d\n", K); return 0; }

[Codeforces 449B] Jzzhu and Cities