HDU - 3974 Assign the task （DFS建树+区间覆盖+单点查询）

1 int cnt = 0;
2 void dfs(int n)
3 {
4     Start[n] = ++cnt;
5     int m = son[n].size();
6     for(int i = 0; i < m; i++)
7         dfs(son[n][i]);//已经用vector son[n] 来存好了每个人的下属
8     End[n] = cnt;
9 }

  1 #include<iostream>
  2 #include<algorithm>
  3 #include<vector>
  4 #include<string>
  5 #include<cstring>
  6 #define lson l,m,rt<<1
  7 #define rson m+1,r,rt<<1|1
  8 using namespace std;
  9 const int N = 50000+5;
 10 vector<int> son[N];
 11 int Start[N], End[N];
 12 int tree[N<<2], lazy[N<<2];
 13 bool vis[N];
 14 int cnt = 0;
 15 void dfs(int n)
 16 {
 17     Start[n] = ++cnt;
 18     int m = son[n].size();
 19     for(int i = 0; i < m; i++)
 20         dfs(son[n][i]);
 21     End[n] = cnt;
 22 }
 23 void PushDown(int rt)
 24 {
 25     if(lazy[rt] != -1)
 26     {
 27         tree[rt<<1] = tree[rt<<1|1] =  lazy[rt<<1|1] = lazy[rt<<1] = lazy[rt];
 28         lazy[rt] = -1;
 29     }
 30 }
 31 void Revise(int L, int R, int C, int l, int r, int rt)
 32 {
 33     if(L <= l && r <= R)
 34     {
 35         lazy[rt] = tree[rt] = C;
 36         return ;
 37     }
 38     PushDown(rt);
 39     int m =l+r >> 1;
 40     if(L <= m) Revise(L,R,C,lson);
 41     if(m < R) Revise(L,R,C,rson);
 42 }
 43 int Query(int L, int l, int r, int rt)
 44 {
 45     if(l == r)
 46     {
 47         return tree[rt];
 48     }
 49     int m = l+r >> 1;
 50     PushDown(rt);
 51     if(L <= m) return Query(L,lson);
 52     else return Query(L,rson);
 53 }
 54 int main()
 55 {
 56     ios::sync_with_stdio(false);
 57     cin.tie(0);
 58     cout.tie(0);
 59     int T;
 60     cin >> T;
 61     for(int i = 1; i <= T; i++)
 62     {
 63         cout << "Case #" << i << ":\n";
 64         int n, u, v;
 65         cnt = 0;
 66         cin >> n;
 67         for(int i = 1; i <= n; i++)
 68             son[i].clear(), vis[i] = 1;
 69         for(int i = 1; i < n; i++)
 70         {
 71             cin >> u >> v;
 72             son[v].push_back(u);//用vector去对应的关系
 73             vis[u] = 0;//如果某个点成为过下属就标记一下 没有标记过的那个人就是Boss(最上级）
 74         }
 75         int pos = -1;
 76         for(int i = 1; i <= n; i++)
 77             if(vis[i])
 78             {
 79                 pos = i;
 80                 break;
 81             }
 82         dfs(pos);//从最上级的人开始递归， 找到每个人对应的区间
 83         memset(tree, -1, sizeof(tree));//因为没有接到任务过的人查询的时候输出-1
 84         memset(lazy, -1, sizeof(lazy));//所以直接memset为-1就好了，不需要再进行特判
 85         int t;
 86         cin >> t;
 87         string str;
 88         int x, y;
 89         while(t--)
 90         {
 91             cin >> str;
 92             if(str[0] == ‘C‘)
 93             {
 94                 cin >> x;
 95                 cout << Query(Start[x],1,cnt,1) << endl;
 96             }
 97             else
 98             {
 99                 cin >> x >> y;
100                 Revise(Start[x],End[x],y,1,cnt,1);
101             }
102         }
103     }
104     return 0;
105 }