Codeforces Gym 100650B Countdown （离线）

题目链接：http://codeforces.com/gym/100650

根据给出的树和d，求出一些结点，这些结点形成子树的第d层结点数应该尽量多，具体要求可以参考题目。

dfs一个结点前保存询问深度的答案，访问完以后减去之前的值就得到答案了。

#include<bits/stdc++.h>
using namespace std;
const int maxn = ;

vector<string> names;
map<string,int> mp;
int id_cnt;
#define se second
#define MP make_pair

int ID(const string & s){
    map<string,int>::iterator i = mp.find(s);
    if(i != mp.end()) return i->se;
    names.push_back(s);
    mp.insert(MP(s,id_cnt));
    return id_cnt++;
}
int deg[maxn];
int head[maxn],nxt[maxn],to[maxn],ecnt;

void addEdge(int u,int v)
{
    to[ecnt] = v;
    nxt[ecnt] = head[u];
    head[u] = ecnt++;
}

int pre[maxn*];
int cnt[maxn*];
int deep[maxn];

struct Node
{
    int d,id;
    bool operator < (const Node & x) const {
        return d < x.d || ( d == x.d && names[id] > names[x.id] );
    }
};

priority_queue<Node> q;

int n,d;
void dfs(int u)
{
    cnt[deep[u]]++;
    int qd = deep[u]+d;
    if(qd < maxn)   pre[u] =  cnt[qd];
    for(int i = head[u]; ~i; i = nxt[i]){
        int v = to[i];
        deep[v] = deep[u]+;
        dfs(v);
    }
    if(qd<maxn){
        int ans = cnt[qd]-pre[u];
        if(ans) q.push(Node{ans,u});
    }
}

void init()
{
    names.clear();
    mp.clear();
    id_cnt = ;
    ecnt = ;
    memset(deg,,sizeof(deg));
    memset(head,-,sizeof(head));
    memset(cnt,,sizeof(cnt));
    while(q.size()) q.pop();
}

char str[];

void read()
{
    scanf("%d%d",&n,&d);
    while(n--){
         int ch; scanf("%s%d",str,&ch);
        int fa = ID(str);
        while(ch--){
            scanf("%s",str);
            int v = ID(str);
            deg[v]++;
            addEdge(fa,v);
        }
    }
}

void topo()
{
    int root;
    n = mp.size();
    for(int i = ; i < n; i++){
        if(deg[i] == ) { root = i; break; }
    }
    deep[root] = ;
    dfs(root);
}

int main()
{
    //freopen("in.txt","r",stdin);
    int T; scanf("%d",&T);
    for(int kas = ; kas <= T; kas++){
        init();
        read();
        topo();
        printf("Tree %d:\n",kas);
        for(int i = ; i <= ; i++){
            if(q.empty()) break;
            Node x = q.top(); q.pop();
            printf("%s %d\n",names[x.id].c_str(),x.d);
            if(i == ){
                int pre = x.d;
                while(q.size()){
                    x = q.top(); q.pop();
                    if(x.d == pre){
                        printf("%s %d\n",names[x.id].c_str(),x.d);
                    }else {
                        break;
                    }
                }
            }
        }
        if(kas != T) putchar('\n');
    }
    return ;
}