HDU 1142 A Walk Through the Forest

记忆化搜索+dfs

#include<iostream>#include<cstdio>#include<cstring>#include<queue>using namespace std;int n,m;int dir[4][2]={1,0,0,1,-1,0,0,-1};int map[1005][1005];bool visit[1005];int dist[1005];int sum[1005];const int INF=0x7fffff;struct node{    int x,y;};queue<int> q;void BFS(){    int i,now;    memset(visit,false,sizeof(visit));    for(i=0;i<=n;i++) dist[i]=INF;    while(!q.empty()) q.pop();    dist[2]=0;    q.push(2);    visit[2]=true;    while(!q.empty())    {        now=q.front();        q.pop();        visit[now]=false;        for(i=1;i<=n;i++)        {            if(dist[i]>dist[now]+map[now][i])            {                dist[i]=dist[now]+map[now][i];                if(visit[i]==false)                {                    q.push(i);                    visit[i]=true;                }            }        }    }}int dfs(int now){    int i,sum1=0;    if(now==2) return 1;    if(sum[now]) return sum[now];    for(i=1;i<=n;i++)    {        if(map[now][i]<INF&&dist[now]>dist[i])        {            if(sum[i]) sum1+=sum[i];            else sum1+=dfs(i);        }    }    sum1+=sum[now];    sum[now]=sum1;    return sum[now];}int main(){    while(scanf("%d",&n)!=EOF&&n)    {        memset(sum,0,sizeof(sum));        scanf("%d",&m);        int s,t,v;        for(int i=0;i<=n;i++)            for(int j=0;j<=n;j++)            {                if(i==j) map[i][j]=0;                else map[i][j]=INF;            }        for(int i=0;i<m;i++)        {            scanf("%d%d%d",&s,&t,&v);            if(v<map[s][t])                map[s][t]=map[t][s]=v;        }        BFS();      //  for(int i=0;i<=n;i++) cout<<dist[i]<<' ';      //  cout<<endl;        int sum1=dfs(1);        printf("%d\n",sum1);    }    return 0;}