acwing搜索与图论（二）堆优化的dijkstra

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

using  namespace std;


typedef pair<int, int> PII;
const int N=10010;
int n,m;
int h[N],e[N],ne[N],w[N],idx;
int dist[N];
bool st[N];
void add(int a,int b,int c){
	e[idx]=b,ne[idx]=h[a],w[idx]=c,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()){
		auto t =heap.top();
		heap.pop();
		
		int ver =t.second;
		int distance=t.first;
		
		
		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();
	
	printf("%d",t);
	return 0;
	
}

其实就是将基础的dijkstra算法简化过程，只将更改过的dist入队，依旧是用的贪心算法，时间复杂度是mlogn，这个是稀疏图。