【例题 6-20 UVA - 1599】Ideal Path

【链接】 我是链接,点我呀:)
【题意】

【题解】

【代码】

/*
  	1.Shoud it use long long ?
  	2.Have you ever test several sample(at least therr) yourself?
  	3.Can you promise that the solution is right? At least,the main ideal
  	4.use the puts("") or putchar() or printf and such things?
  	5.init the used array or any value?
  	6.use error MAX_VALUE?
*/
#include <bits/stdc++.h>
using namespace std;

const int N = 1e5;

int n,m,dis[N+10];
int vis[N+10];
vector < pair<int,int> > g[N+100];	
queue <int> dl;
int a[N+10];

int main(){
	#ifdef LOCAL_DEFINE
	    freopen("F:\\c++source\\rush_in.txt", "r", stdin);
	#endif
	ios::sync_with_stdio(0),cin.tie(0);
	
	while (cin >> n >> m){
		memset(vis,0,sizeof vis);
		for (int i = 1;i <= n+1;i++) a[i] = (int) 1e9+7;
		for (int i = 1;i <= n;i++) g[i].clear();
	 	for (int i = 1;i <= m;i++){
			int x,y,z;
			cin >>x>>y>>z;
			g[x].push_back(make_pair(y,z));
			g[y].push_back(make_pair(x,z));
	 	}

		memset(dis,255,sizeof dis);
		dis[n] = 0;
		dl.push(n);
		while (!dl.empty()){
		 	int x = dl.front();
		 	dl.pop();
		 	for (int i = 0;i < (int)g[x].size();i++){
				int y = g[x][i].first;
				if (dis[y]==-1){
				 	dis[y] = dis[x] + 1;
				 	dl.push(y);
				}
		 	}
		}

		vis[1] = 1;
		dl.push(1);
		while (!dl.empty()){
			int x = dl.front();
			dl.pop();
			if (vis[x]>a[dis[x]+1]) continue; //vis[x]就是路径中到x的前一条边的最小权值,如果它不是前一条边的最小字典序就跳过
			
			int mi = (int) 1e9 + 10;
			for (int i = 0;i < (int) g[x].size();i++){
			 	int y = g[x][i].first;
			 	if (dis[y]==dis[x]-1){
					mi = min(mi,g[x][i].second);			 	 	
			 	}
			}
			
			a[dis[x]] = min(mi,a[dis[x]]);
			for (int i = 0;i < (int) g[x].size();i++){
			 	int y = g[x][i].first;
			 	if (dis[y]==dis[x]-1 && g[x][i].second==mi){
			 		if (!vis[y]) dl.push(y);	 	 	
			 		if(!vis[y] || vis[y]>mi) vis[y] = mi;
			 	}
			}
		}

		cout << dis[1] << endl;
		for (int i = dis[1];i >= 1;i--) {
			cout << a[i];
			if (i==1) cout << endl;else cout << ' ';
		}
	}


	return 0;
}