堆优化版迪杰斯特拉

代码

#include<iostream>
#include<algorithm>
#include<cstring>
#include<queue>
using namespace std;
const int N = 150010;
const int M = 150010;
int h[N],e[M],ne[M],w[M];
int n,m;
int idx;	
int dist[N],vis[N];
typedef pair<int,int> pii;


void add(int x, int y, int z){
	w[idx] = z;
	e[idx] = y;
	ne[idx] = h[x];
	h[x] = idx++;
}

void dij(){
	memset(dist,0x3f,sizeof dist);
	priority_queue<pii,vector<pii>, greater<pii>>q;
	
	dist[1] = 0;
	q.push({0,1});
	while(q.size()){
		auto it = q.top();
		q.pop();
		int d = it.first;
		int x = it.second;
		if(vis[x]) continue;//防止重边 
		vis[x] = 1;
		for(int i = h[x]; i != - 1; i = ne[i]){
			int j = e[i];//i是下标，e[i]才是对应的点
			if(dist[j] > d + w[i]){
				dist[j] = d + w[i];
				q.push({dist[j],j});
			}
		}
	}
}

int main(){
	cin >> n >> m;
	int x,y,z;
	memset(h,-1,sizeof h);//记得初始化
	for(int i = 1; i <= m; i++){
		cin >> x >> y >> z;
		add(x,y,z);
	}
	dij();
	if(dist[n] == 0x3f3f3f3f) cout << -1;
	else cout <<  dist[n];
	return 0;
}