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  1. #include <stdio.h>
  2. #include <malloc.h>
  3.  
  4. struct TreeNode {
  5. 	int val;
  6. 	struct TreeNode* left, * right;
  7. };
  8.  
  9. int tree_size(/*struct TreeNode* tree*/) { return 7; }
  10.  
  11. int* preorder_(struct TreeNode* tn, int* v) {
  12.     *v++ = tn->val;
  13. 	if (tn->left) v = preorder_(tn->left, v);
  14. 	if (tn->right) v = preorder_(tn->right, v);
  15.  
  16. 	return v;
  17. }
  18.  
  19. int* preorder(struct TreeNode* tn) {
  20. 	if (tn) {
  21. 		int* v = malloc(tree_size(/*tn*/) * sizeof(int));
  22. 		preorder_(tn, v);
  23. 		return v;
  24. 	} else {
  25. 		return NULL;
  26. 	}
  27. }
  28.  
  29. int main(void) {
  30. 	//    4
  31. 	//  2   5
  32. 	// 1 3 6 7
  33. 	struct TreeNode 
  34. 	    lleft = {1}, lright = {3}, leftroot = {2, &lleft, &lright}, 
  35. 		rleft = {6}, rright = {7}, rightroot = {5, &rleft, &rright}, 
  36. 		root = {4, &leftroot, &rightroot};
  37. 	int *v, i;
  38.  
  39. 	v = preorder(&root);
  40. 	for (i = 0; i < tree_size(/*tn*/); i++) {
  41. 		printf("%d ", v[i]); // 4 2 1 3 5 6 7
  42. 	}
  43. 	free(v);
  44.  
  45. 	return 0;
  46. }
  47.  
Success #stdin #stdout 0s 2292KB
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Standard input is empty
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4 2 1 3 5 6 7
https://ideone.com/LCV8uc
http://stackoverflow.com/questions/37481526/preorder-tree-traversal-function-which-returns-an-array-of-integers-in-c
language:
C (gcc 8.3)
created:
8 years ago
visibility:
public

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