DIJKSTRA
#include <iostream>
#include <cstring>
#include <queue>
using namespace std;
const int N = 150010;
typedef pair<int, int> PII;
int h[N], e[N], ne[N], w[N], idx;
int n, m, dist[N], st[N];
int add(int a, int b, int c)
{
w[idx] = c;
e[idx] = b;
ne[idx] = h[a];
h[a] = idx++;
}
int dijkstra()
{
memset(dist, 0x3f, sizeof dist);
dist[1] = 0;
priority_queue<PII, vector<PII>, greater<PII>> heap;
heap.push({0, 1});
while (heap.size())
{
PII k = heap.top();
heap.pop();
if (st[k.second])
continue;
st[k.second] = 1;
for (int i = h[k.second]; i != -1; i = ne[i])
{
int j = e[i];
if (dist[j] > k.first + w[i])
{
dist[j] = w[i] + k.first;
heap.push({dist[j], j});
}
}
}
if (dist[n] == 0x3f3f3f3f)
return -1;
return dist[n];
}
int main()
{
cin >> n >> m;
memset(h, -1, sizeof h);
while (m–)
{
int a, b, c;
scanf(“%d%d%d”, &a, &b, &c);
add(a, b, c);
}
cout << dijkstra() << endl;
return 0;
}
