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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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