Codeforces449A Jzzhu and Chocolate && 449B Jzzhu and Cities

#pragma warning(disable:4996)
#include <iostream>
#include <cstdio>
#include <vector>
#include <cstring>
#include <string>
#include <algorithm>
#include <cmath>
#include <queue>
using namespace std;

#define ll long long
#define maxn 105000
#define inf 10000000000000000LL

int n, m, k;

struct Edge
{
	int v;
	ll w;
	Edge(int vi, ll wi) : v(vi), w(wi){}
	Edge(){}
};

vector<Edge>G[maxn];
ll dis2[maxn];
ll ans = 0;

ll d[maxn];
bool in[maxn];
void spfa()
{
	memset(d, 0x3f, sizeof(d));
	memset(in, 0, sizeof(in));
	queue<int> que;
	que.push(1); in[1] = true;
	d[1] = 0;
	while (!que.empty()){
		int u = que.front(); que.pop(); in[u] = false;
		for (int i = 0; i < G[u].size(); i++){
			int v = G[u][i].v; ll w = G[u][i].w;
			if (d[u] + w < d[v]){
				d[v] = d[u] + w;
				if (!in[v]) que.push(v), in[v] = true;
			}
		}
	}
}

ll d2[maxn];
bool upd[maxn];

void spfa2()
{
	memset(d2, 0x3f, sizeof(d2));
	memset(in, 0, sizeof(in));
	queue<int> que;
	que.push(1); d2[1] = 0; in[1] = true;
	for (int i = 2; i <= n; i++){
		if (dis2[i] < d[i]){
			que.push(i); in[i] = true; d2[i] = dis2[i];
		}
	}
	while (!que.empty()){
		int u = que.front(); que.pop(); in[u] = false;
		for (int i = 0; i < G[u].size(); i++){
			int v = G[u][i].v; ll w = G[u][i].w;
			if (d2[u] + w < d2[v]){
				d2[v] = d2[u] + w;
				if (!in[v]) que.push(v), in[v] = true;
				if (upd[v]) {
					++ans; upd[v] = false;
				}
			}
			else if (d2[u] + w == d2[v]){
				if (upd[v]) {
					++ans; upd[v] = false;
				}
			}
		}
	}
}

int main()
{
	while (cin >> n >> m >> k){
		for (int i = 0; i <= n; i++) G[i].clear();
		memset(dis2, 0x3f, sizeof(dis2));
		ans = 0;
		int ui, vi; ll wi;
		for (int i = 0; i < m; i++){
			scanf("%d%d%I64d", &ui, &vi, &wi);
			G[ui].push_back(Edge(vi, wi));
			G[vi].push_back(Edge(ui, wi));
		}
		spfa();
		memcpy(dis2, d, sizeof(dis2));
		memset(upd, 0, sizeof(upd));
		int si; ll yi;
		for (int i = 0; i < k; i++){
			scanf("%d%I64d", &si, &yi);
			if (dis2[si] <= yi) ++ans;
			else {
				dis2[si] = yi; 
				if (upd[si]) {
					++ans;
				}
				upd[si] = true;
			}
		}
		spfa2();
		cout << ans << endl;
	}
	return 0;
}