-
Notifications
You must be signed in to change notification settings - Fork 0
/
144 Binary Tree Preorder Traversal.c
104 lines (87 loc) · 2.11 KB
/
144 Binary Tree Preorder Traversal.c
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
/**
* Definition for a binary tree node.
* struct TreeNode {
* int val;
* struct TreeNode *left;
* struct TreeNode *right;
* };
*/
#define MAX_STACK_SIZE 100
typedef struct stack
{
struct TreeNode * arr[MAX_STACK_SIZE];
int top;
}Stack;
int isStackFull(Stack * preorder_stack)
{
if(preorder_stack->top == MAX_STACK_SIZE-1)
return 1;
else
return 0;
}
int isStackEmpty(Stack * preorder_stack)
{
if(preorder_stack->top == -1)
return 1;
else
return 0;
}
void push(Stack * preorder_stack, struct TreeNode * element)
{
if(isStackFull(preorder_stack))
{
return;
}
preorder_stack->arr[++(preorder_stack->top)] = element;
}
struct TreeNode * pop(Stack * preorder_stack)
{
if(isStackEmpty(preorder_stack))
return NULL;
struct TreeNode * ret_val = preorder_stack->arr[preorder_stack->top];
(preorder_stack->top)--;
return ret_val;
}
int nodes_count(struct TreeNode * root)
{
int count = 0;
struct TreeNode * trav_ptr = root;
if(trav_ptr != NULL)
{
int left_count = nodes_count(trav_ptr->left);
int right_count = nodes_count(trav_ptr->right);
return left_count + right_count + 1;
}
else
{
return 0;
}
}
/**
* Note: The returned array must be malloced, assume caller calls free().
*/
int* preorderTraversal(struct TreeNode* root, int* returnSize)
{
Stack preorder_stack;
preorder_stack.top = -1;
int no_of_nodes = nodes_count(root);
int * ret_arr = (int *)malloc(sizeof(int)*no_of_nodes);
int ret_arr_index = 0;
*returnSize = no_of_nodes;
struct TreeNode * trav_ptr = root;
while((trav_ptr!=NULL) || (!isStackEmpty(&preorder_stack)))
{
if(trav_ptr != NULL)
{
ret_arr[ret_arr_index++] = trav_ptr->val;
push(&preorder_stack, trav_ptr);
trav_ptr = trav_ptr->left;
}
else if(trav_ptr == NULL)
{
trav_ptr = pop(&preorder_stack);
trav_ptr = trav_ptr->right;
}
}
return ret_arr;
}