POJ 3321 DFS序+线段树

单点修改树中某个节点,查询子树的性质.DFS序 子树序列一定在父节点的DFS序列之内,所以可以用线段树维护.

   1:  /*

   2:  DFS序 +线段树

   3:  */

   4:   

   5:  #include <cstdio>

   6:  #include <cstring>

   7:  #include <cctype>

   8:  #include <algorithm>

   9:  #include <vector>

  10:  #include <iostream>

  11:  using namespace std;

  12:   

  13:  #define LL(a)   a<<1

  14:  #define RR(a)   a<<1|1

  15:   

  16:  const int MaxL = 200002;

  17:   

  18:  int pre[MaxL];  // first travel

  19:  int nxt[MaxL];  // nxt travel

  20:  bool vis[MaxL];

  21:  int N;

  22:  vector<vector<int> > E(MaxL);

  23:   

  24:  struct Seg_tree

  25:  {

  26:      int left, right;

  27:      int sum;

  28:  } tt[MaxL<<2];

  29:   

  30:   

  31:  void PushUp(int idx)

  32:  {

  33:      tt[idx].sum = tt[LL(idx)].sum + tt[RR(idx)].sum;

  34:  }

  35:   

  36:  void build(int l,int r,int idx)

  37:  {

  38:      tt[idx].left = l, tt[idx].right = r;

  39:      tt[idx].sum = r-l+1;

  40:      if (l == r) return ;

  41:      int m = (l + r) >> 1;

  42:      build(l,m, LL(idx));

  43:      build(m+1, r, RR(idx));

  44:  }

  45:   

  46:  void update(int p, int idx = 1)

  47:  {

  48:      if(p == tt[idx].left && p == tt[idx].right)

  49:      {

  50:          tt[idx].sum ^=1;

  51:          return ;

  52:      }

  53:      int mid = (tt[idx].left + tt[idx].right)>>1;

  54:      if(p <= mid) update(p, LL(idx));

  55:      else update(p, RR(idx));

  56:      PushUp(idx);

  57:  }

  58:   

  59:  int query(int l, int r, int idx = 1)

  60:  {

  61:      if(l == tt[idx].left && r ==tt[idx].right)

  62:          return tt[idx].sum;

  63:      int mid = (tt[idx].left + tt[idx].right)>>1;

  64:      if(r <= mid) return query(l,r, LL(idx));

  65:      else if(l> mid) return query(l,r, RR(idx));

  66:      else

  67:          return query(l, mid, LL(idx))+ query(mid+1, r, RR(idx));

  68:  }

  69:   

  70:  int mark = 1;

  71:  void dfs( int a)

  72:  {

  73:      vis[a] = 1;

  74:      pre[a] = mark++;

  75:      for(int i=0; i<E[a].size(); i++)

  76:      {

  77:          if(!vis[E[a][i]])

  78:              dfs(E[a][i]);

  79:      }

  80:      nxt[a] = mark++;

  81:  }

  82:  int main()

  83:  {

  84:  //    freopen("1.txt","r",stdin);

  85:      memset(pre, 0, sizeof(pre));

  86:      memset(nxt, 0 ,sizeof(nxt));

  87:      memset(vis, 0 ,sizeof(vis));

  88:   

  89:      scanf("%d", &N);

  90:      for(int i=1; i<N; i++)

  91:      {

  92:          int a,b;

  93:          scanf("%d%d", &a,&b);

  94:          E[a].push_back(b);

  95:          E[b].push_back(a);

  96:      }

  97:      dfs(1);

  98:   

  99:      N*=2;

 100:      build(1, N, 1);

 101:      int M;

 102:      scanf("%d", &M);

 103:      for(int i=1; i<=M; i++)

 104:      {

 105:          char c;

 106:          int a;

 107:          scanf("%s", &c);

 108:          scanf("%d",&a);

 109:          if(c =='Q')

 110:          {

 111:              cout<<query(pre[a],nxt[a], 1) /2<<endl;

 112:          }

 113:          else

 114:          {

 115:              update(pre[a],1);

 116:              update(nxt[a],1);

 117:          }

 118:      }

 119:      return 0;

 120:  }

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