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OI-codes/Luogu/P1342/P1342.cpp

64 lines
1.7 KiB
C++

#include <bits/stdc++.h>
using namespace std;
int n, m, u, v;
long long w, dist1[100005], dist2[100005], ans;
vector<pair<int, long long>> g1[100005], g2[100005];
bool st1[100005], st2[100005];
void dijkstra1() {
memset(dist1, 0x3f, sizeof(dist1));
dist1[1] = 0;
priority_queue<pair<long long, int>, vector<pair<long long, int>>, greater<pair<long long, int>>> q;
q.push(make_pair(0, 1));
while (!q.empty()) {
auto t = q.top();
q.pop();
if (st1[t.second]) continue;
for (auto i : g1[t.second]) {
if (dist1[i.first] > t.first + i.second) {
dist1[i.first] = t.first + i.second;
q.push(make_pair(dist1[i.first], i.first));
}
}
st1[t.second] = true;
}
}
void dijkstra2() {
memset(dist2, 0x3f, sizeof(dist2));
dist2[1] = 0;
priority_queue<pair<long long, int>, vector<pair<long long, int>>, greater<pair<long long, int>>> q;
q.push(make_pair(0, 1));
while (!q.empty()) {
auto t = q.top();
q.pop();
if (st2[t.second]) continue;
for (auto i : g2[t.second]) {
if (dist2[i.first] > t.first + i.second) {
dist2[i.first] = t.first + i.second;
q.push(make_pair(dist2[i.first], i.first));
}
}
st2[t.second] = true;
}
}
int main() {
std::ios::sync_with_stdio(false);
cin >> n >> m;
for (int i = 1; i <= m; i++) {
cin >> u >> v >> w;
g1[u].push_back(make_pair(v, w));
g2[v].push_back(make_pair(u, w));
}
dijkstra1();
dijkstra2();
for (int i = 2; i <= n; i++) {
ans += dist1[i] + dist2[i];
}
cout << ans << endl;
return 0;
}