ソースコード
#include <bits/stdc++.h>
#define GET_MACRO(_1,_2,_3,_4,_5,_6,_7,_8,NAME,...) NAME
#define pr(...) cerr<< GET_MACRO(__VA_ARGS__,pr8,pr7,pr6,pr5,pr4,pr3,pr2,pr1)(__VA_ARGS__) <<endl
#define pr1(a) (#a)<<"="<<(a)<<" "
#define pr2(a,b) pr1(a)<<pr1(b)
#define pr3(a,b,c) pr1(a)<<pr2(b,c)
#define pr4(a,b,c,d) pr1(a)<<pr3(b,c,d)
#define pr5(a,b,c,d,e) pr1(a)<<pr4(b,c,d,e)
#define pr6(a,b,c,d,e,f) pr1(a)<<pr5(b,c,d,e,f)
#define pr7(a,b,c,d,e,f,g) pr1(a)<<pr6(b,c,d,e,f,g)
#define pr8(a,b,c,d,e,f,g,h) pr1(a)<<pr7(b,c,d,e,f,g,h)
using namespace std;
using Int = long long;
using _int = int;
using ll = long long;
using Double = long double;
const Int INF = (1LL<<55)+1e9; // ~ 3.6 * 1e16
const Int mod = (1e9)+7;
const Double EPS = 1e-8;
const Double PI = 6.0 * asin((Double)0.5);
using P = pair<Int,Int>;
using T = tuple<Int,Int,Int>;
template<class T> T Max(T &a,T b){return a=max(a,b);}
template<class T> T Min(T &a,T b){return a=min(a,b);}
ostream& operator<<(ostream& o,P p){return o<<"("<<p.first<<","<<p.second<<")";}
ostream& operator<<(ostream& o,T t){return o<<"("<<get<0>(t)<<","<<get<1>(t)<<","<<get<2>(t)<<")";}
istream& operator>>(istream& i,P &p){return i>>p.first>>p.second;}
template<class T> ostream& operator<<(ostream& o,vector<T> &a){Int i=0;for(auto t:a)o<<(i++?" ":"")<<t;return o;}
template<class T> istream& operator>>(istream& i,vector<T> &a){for(auto &t:a)i>>t;return i;}
template<class T> void prArr(T a,string s=" "){Int i=0;for(auto t:a)cout<<(i++?s:"")<<t;cout<<endl;}
class Dijkstra{
public:
typedef tuple<Int,Int> T;
long long INF = 1LL<<55;
Int V;
vector<vector<T> > G;
Dijkstra():V(-1){}
Dijkstra(Int V):V(V),G(V){}
void add_edge(Int a,Int b,Int c){
assert(a >= 0 && b >= 0);
assert(a < V && b < V);
G[a].push_back(T(b,c));
G[b].push_back(T(a,c));
}
vector<Int> dijkstra(vector<P> start){
vector<Int> D(V,-INF);
vector<Int> visited(V,0);
priority_queue<T> Q;
for(auto p:start){
Int s = p.first-1;
Int d = p.second;
Q.push(T(d,s));
Max(D[s],d);
}
while(!Q.empty()){
Int cost, pos;
tie(cost,pos) = Q.top(); Q.pop();
assert(!visited[pos] || D[pos] >= cost);
if(visited[pos]++) continue;
for(auto t:G[pos]){
Int to = get<0>(t);
Int ncost = cost - get<1>(t);
if(D[to] >= ncost) continue;
D[to] = ncost;
Q.push(T(ncost,to));
}
}
return D;
}
};
signed main(){
srand((unsigned)time(NULL));
cin.tie(0);
ios_base::sync_with_stdio(0);
cout << fixed << setprecision(12);
Int n, m, K;
cin>>n>>m>>K;
Dijkstra D(n);
for(Int i=0;i<m;i++){
Int a,b,c;
cin>>a>>b>>c; a--,b--;
D.add_edge(a, b, c);
}
vector<P> start(K);
cin>>start;
vector<Int> DD = D.dijkstra(start);
Int ans = 0;
for(Int i=0;i<n;i++)
if(DD[i] >= 0) ans++;
cout<<ans<<endl;
return 0;
}