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  1. #include <iostream>
  2.  
  3. template <typename T>
  4. struct Node {
  5.     T value;
  6.     Node<T> *left, *right, *next_sibling;
  7. };
  8.  
  9. template <typename T>
  10. void link_siblings(Node<T> *root) {
  11.     //   * -> * <upper
  12.     // /   \
  13.     // * -> * <lower
  14.     // ^ level_start
  15.     Node<T> *upper = root, *lower = nullptr, *level_start = nullptr;
  16.     while (upper) {
  17.         for (auto child : {upper->left, upper->right}) {
  18.             if (child) {
  19.                 if (lower) lower->next_sibling = child;
  20.                 else       level_start         = child;
  21.                 lower = child;
  22.             }
  23.         }
  24.  
  25.         if (upper->next_sibling) {
  26.             upper = upper->next_sibling;
  27.         } else {
  28.             upper = level_start;
  29.             level_start = lower = nullptr;
  30.         }
  31.     }
  32. }
  33.  
  34. int main() {
  35.     //        0
  36.     //   1        4
  37.     // 2   3         5
  38.     constexpr int N = 6;
  39.     Node<int> nodes[N];
  40.     int lchildren[N] = {1,  2, -1, -1, -1, -1};
  41.     int rchildren[N] = {4,  3, -1, -1,  5, -1};
  42.     for (int i = 0; i < N; i++) {
  43.         nodes[i].value = i;
  44.         nodes[i].left = nodes[i].right = nodes[i].next_sibling = nullptr;
  45.         if (lchildren[i] >= 0) nodes[i].left  = &nodes[lchildren[i]];
  46.         if (rchildren[i] >= 0) nodes[i].right = &nodes[rchildren[i]];
  47.     }
  48.     link_siblings(&nodes[0]);
  49.     for (int i = 0; i < N; i++) {
  50.         auto sibling = nodes[i].next_sibling;
  51.         int sibling_value = sibling ? (sibling->value) : -1;
  52.         std::cout << nodes[i].value << " => " << sibling_value << "\n";
  53.     }
  54.     return 0;
  55. }
Success #stdin #stdout 0s 3456KB
comments (?)
stdin 
Standard input is empty
stdout 
0 => -1
1 => 4
2 => 3
3 => 5
4 => -1
5 => -1
https://ideone.com/cMFkBF
language:
C++14 (gcc 8.3)
created:
10 years ago
visibility:
secret

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