調了一天，囧！第一次寫 lazy 更新線段樹，結果在查詢和 add 時沒有考慮到我用了區間 lazy 更新。後面在增加 lazy 更新處理代碼時，將 bitmap 作為 color 傳進去。導致 add 函數邏輯不正確。
本題還有一個坑，要考慮輸入參數的大小。L 參數可能比 R 參數大！！

# include <iostream>
# include <algorithm>
# include <memory.h>
# include <vector>
# include <assert.h>

using namespace std;

const int maxn = 100010;

struct Num {
  int val;
  int pos;
  bool operator <(const Num &a)const {
    return val < a.val;
  }
}num[maxn];

int n, nT, nQ; //L, T, Q (O is always worse)


int find_index(int num) {
  int sum = 0;
  while (num > 1) {
    sum += 1;
    num = num >> 1;
  }
  return sum;
}


struct Segment {
  // 因為不需要修改
  struct _nod{
    int bitmap, lazy;
    int l, r;
  } TreeNode[maxn << 2]; //bug 之前開到 [maxn <<1] 直接報 runtime error 
  
  void init() {
    memset(TreeNode, 0, sizeof(TreeNode));
  }

  void build(int index, int l, int r) {
    int mid = (l+r) >> 1;
    TreeNode[index].l = l; TreeNode[index].r = r; TreeNode[index].bitmap = 1 << 1; TreeNode[index].lazy = 0;
    if (l == r)
      return;
    build(index <<1, l, mid); build(index << 1|1, mid+1, r);
  }


  void remove_lazy(int index) {
    int mid = (TreeNode[index].l + TreeNode[index].r) >> 1;

    if (TreeNode[index].lazy == 1) {
      add(index<<1, TreeNode[index].l, mid, find_index(TreeNode[index].bitmap)); // 不能將 TreeNode[index].bitmap 傳進去啊 
      add(index<<1|1, mid+1, TreeNode[index].r, find_index(TreeNode[index].bitmap));      
      TreeNode[index].lazy = 0;
    }
    
    /*
    if (TreeNode[index].lazy == 1) {
      TreeNode[index<<1].bitmap = TreeNode[index].bitmap; TreeNode[index<<1|1].bitmap = TreeNode[index].bitmap;
      TreeNode[index<<1].lazy = 1;  TreeNode[index<<1|1].lazy = 1;
      TreeNode[index].lazy = 0;
    }
    */
  }

  
  void add(int index, int cl, int cr, int color) {
    
    int mid = (TreeNode[index].l + TreeNode[index].r) >> 1;
    
    if (TreeNode[index].bitmap == (1<<color)) {
      return;
    }
    
    if (TreeNode[index].l == cl and cr == TreeNode[index].r ) {
      TreeNode[index].bitmap = 1 << color;
      TreeNode[index].lazy = cl == cr? 0: 1 ;
      return;
    }

    remove_lazy(index);
    
    if (mid >= cr) {
      add(index <<1, cl, cr, color);
    }
    
    else if (cl > mid) {
      add(index <<1|1, cl, cr, color);
    }
    else {
      add(index <<1, cl, mid, color);
      add(index <<1|1, mid+1, cr, color);
    }
    
    TreeNode[index].bitmap = TreeNode[index<<1].bitmap | TreeNode[index<<1|1].bitmap;
  }
  
  int query(int index, int cl, int cr) {
    int mid=0;
    /*
    if (TreeNode[index].lazy)
      return TreeNode[index].bitmap;
    */
    
    if (TreeNode[index].l == cl and cr == TreeNode[index].r)
       return TreeNode[index].bitmap;
    
    mid = (TreeNode[index].l + TreeNode[index].r) >> 1;

    remove_lazy(index);
    
    if (mid >= cr)
      return query(index<<1, cl, cr);
    else if (cl> mid)
      return query(index<<1|1, cl, cr);
    else
      return query(index<<1, cl, mid) | query(index<<1|1, mid+1, cr);
  }
    
}T;


int get_bits(int x) {
  int sums = 0;
   while (x >0){
     sums += x%2;
     x = x/2;
   }
   return sums;
}


int main(int argc, char* argv[]){

  int l, r, color;
  char ch = ‘Z‘;
  
  scanf("%d%d%d", &n, &nT, &nQ);
    
  T.init();
  T.build(1, 1, n);
    
  while(nQ--) {
    getchar(); 
    scanf("%c", &ch);
    if (‘C‘ == ch) {
      scanf("%d%d%d", &l, &r, &color);
      if (l > r)
        swap(l, r);
      
      T.add(1, l, r, color);
    }
    if (‘P‘ == ch)  {
      scanf("%d%d", &l, &r);
      if (l > r)
        swap(l, r);
      printf("%d\n", get_bits(T.query(1, l, r))); 
    }
  }
  return 0;
}


 

poj 2777