850. Dijkstra求最短路 II

代码：

#include<algorithm>
#include<iostream>
#include<cstring>
#include<queue>
#include<cmath>

using namespace std;
//用pair存储编号和距离
typedef pair<int,int> PII;
 
int n,m;
const int N = 1000010;
int e[N],w[N],ne[N],h[N],idx; 
int dist[N];
bool st[N];
//存在重边和自环

void add(int a,int b,int c){
	e[idx] = b;
	w[idx] = c;
	ne[idx] = h[a];
	h[a] = idx++;
}

int dijkstra(){
	memset(dist,0x3f,sizeof dist);
	dist[1] = 0;
	//n次迭代 
	priority_queue<PII,vector<PII>,greater<PII>> heap;
	heap.push({0,1});
	
	while(heap.size()){
		auto t = heap.top();
		heap.pop();
		
		int distance = t.first;
		int ver = t.second;
		if(st[ver]) continue;
		st[ver] = true;
		for(int i=h[ver];i!=-1;i=ne[i]){
			int j=e[i];
			if(dist[j] > distance + w[i]){
				dist[j] = distance + w[i];
				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;
		cin>>a>>b>>c;
		add(a,b,c);
	}
	int t = dijkstra();
	
	cout<<t<<endl;
	return 0;
}