ChonSu [ZOJ 2684]

http://acm.zju.edu.cn/onlinejudge/showProblem.do?problemId=1684

//重新建树，求两点间最短距离
const int MM = 11111;
#define inf 0x3f3f3f3f
#define debug puts("wrong")
typedef long long int64;
int num[MM], N, tot;
int chd[MM], len; //节点的儿子个数
bool vis[MM];
vector<int>edge[MM];
struct Info{int node,step;};

void get_data() {
    int i,j,k;
    scanf("%d",&N);
    for(i=0;i<MM;i++) edge[i].clear();
    for(i=1;i<N;i++) scanf("%d",&num[i]);
    tot=N+1;
}
int dfs(int u) {
    int i,j,k,v,res;
    vis[u]=true;
    for(i=0;i<edge[u].size();i++) {
        v=edge[u][i];  
        if(v<=N) continue; len++;
        if(chd[v]==1) return v;
        if(!vis[v]) return dfs(v);
    }
}
queue<Info>que;
int bfs(int x,int y) {
    if(x==y) return 0;
    int i,j,k,a,b; Info tmp,tt;
    tmp.node=x, tmp.step=0;
    memset(vis,false,sizeof(vis));
    vis[x]=true;
    while(!que.empty()) que.pop();
    que.push(tmp);
    while(!que.empty()) {
        tmp=que.front(); que.pop();
        a=tmp.node; b=tmp.step;
        for(i=0;i<edge[a].size();i++) {
            int v=edge[a][i];
            if(!vis[v]) {
                vis[v]=true;
                tt.node=v; tt.step=b+1;
                if(v==y) return tt.step;
                else que.push(tt);
            }
        }
    }
    return 0;
}
void slove() {
    int i,j,k,tmp,tt=1,x,y;
    memset(chd,0,sizeof(chd));
    for(j=1;j<num[1];j++) {
        //printf("%d %d\n",tt,tot);
        edge[tt].push_back(tot);
        edge[tot].push_back(tt);
        chd[tt]++;  tt=tot; tot++; 
    }
    edge[tt].push_back(2);
    edge[2].push_back(tt);
    chd[tt]++;
    //printf("%d %d %d\n",chd[1],chd[7],chd[8]);
    for(i=2;i<N;i++) {
        memset(vis,false,sizeof(vis));
        for(j=0;j<=N;j++) vis[j]=true;
        len=0; tmp=dfs(i); 
        //    printf("%d\n",tmp);
        if(len==num[i]-1) {
            edge[tmp].push_back(i+1);
            edge[i+1].push_back(tmp);
            chd[tmp]++;
        }
        else {
            for(j=len+1;j<num[i];j++) {
                edge[tmp].push_back(tot);
                edge[tot].push_back(tmp);
                chd[tmp]++; tmp=tot; tot++; 
            }
            edge[tmp].push_back(i+1);
            edge[i+1].push_back(tmp);
            chd[tmp]++;
        }
        //    if(i==3) printf("%d %d %d %d\n",i,tot,tmp,len);
    }
//    for(i=0;i<edge[11].size();i++) printf("%d ",edge[11][i]); printf("\n");
    scanf("%d%d",&x,&y); 
    printf("%d\n",bfs(x,y));
}
int main() {
    int ca; scanf("%d",&ca);
    while(ca--) get_data(),slove();
    return 0;
}