UVa1599 - Ideal Path

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#include<cstdio>#include<cstring>#include<vector>#include<queue>using namespace std;const int maxn=100010;const int inf=1<<30;int n,vis[maxn],d[maxn];vector<int> g[maxn],ans;struct way{    int u,v,c;    way(int u=0,int v=0,int c=0):u(u),v(v),c(c){}};vector<way> ways;void build(int u,int v,int c){    ways.push_back(way(u,v,c));    int i=(int)ways.size()-1;    g[u].push_back(i);}void rev_bfs(){    memset(vis,0,sizeof(vis));    d[n-1]=0;    vis[n-1]=true;    queue<int>q;    q.push(n-1);    while(!q.empty()){        int v=q.front();        q.pop();        for(int i=0;i<g[v].size();i++)        {            int e=g[v][i];            int u=ways[e].v;            if(!vis[u]){                vis[u]=true;                d[u]=d[v]+1;                q.push(u);            }        }    }}void bfs(){    memset(vis,0,sizeof(vis));    ans.clear();    vis[0]=true;    vector<int>next;    next.push_back(0);    for(int i=0;i<d[0];i++){        int min_color=inf;        for(int j=0;j<next.size();++j){            int u=next[j];            for(int k=0;k<g[u].size();++k)        {            int e=g[u][k];            int v=ways[e].v;            if(d[u]==d[v]+1)                min_color=min(min_color,ways[e].c);        }    }    ans.push_back(min_color);    vector<int> next2;    for(int j=0;j<next.size();j++){        int u=next[j];        for(int k=0;k<g[u].size();k++){            int e=g[u][k];            int v=ways[e].v;            if(d[u]==d[v]+1&&!vis[v]&&ways[e].c==min_color){                vis[v]=true;                next2.push_back(v);            }        }    }    next=next2;    }    printf("%d\n",(int)ans.size());    for(int i=0;i<ans.size();i++){        if(i) printf(" ");        printf("%d", ans[i]);    }    printf("\n");}int main(){    int u,v,c,m;    while(~scanf("%d%d",&n,&m)){        ways.size();        for(int i=0;i<n;i++)            g[i].clear();        while(m--){            scanf("%d%d%d",&u,&v,&c);            build(u-1,v-1,c);            build(v-1,u-1,c);        }        rev_bfs();        bfs();    }    return 0;}
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