hihocoder 1093：最短路（SPFA）

hihocoder 1093

题解：spfa裸题目，存在重复的边和环没关系。

代码：

#include <bits/stdc++.h>
using namespace std;
typedef pair<int,int>pii;
int const inf = 0x7f7f7f7f;
int const N = 100000 + 10;
int const M = 1000000 + 10;
int n,m,s,t,d[N];
struct Edge
{
	int from,to,dist;
	Edge(){}
	Edge(int f,int t,int d):from(f),to(t),dist(d){}
};
vector<Edge>G[N];
queue<int>q;
int spfa(int s){
	for(int i=1;i<=n;i++)	d[i] = inf;
	int vis[N];
	memset(vis,0,sizeof(vis));
	d[s] = 0;
	q.push(s);
	while(!q.empty()){
		int u = q.front();	q.pop();
		vis[u] = false;
		for(int i=0;i<G[u].size();i++){
			Edge e = G[u][i];
			if(d[e.to] > d[e.from] + e.dist){
				d[e.to] = d[e.from] + e.dist;
				if(!vis[e.to]){
					vis[e.to] = true;
					q.push(e.to);
				}
			}
		}
	}
	return d[t];
}
int main(){
	scanf("%d%d%d%d",&n,&m,&s,&t);
	for(int i=1;i<=m;i++){
		int from,to,dist;
		scanf("%d%d%d",&from,&to,&dist);
		G[from].push_back(Edge(from,to,dist));
		G[to].push_back(Edge(to,from,dist));
	}
	printf("%d\n",spfa(s));
	return 0;
}