compCode-II/Iterative_ Tree_traversals.cpp at master · vismit2000/compCode-II · GitHub

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
09/08/2019

#Iterative InOrder, PreOrder and PostOrder Traversals

struct node
{
    int val;
    node *left, *right;
    node(int x)
    {
        val = x;
        left = right = NULL;
    }
};

##InOrder

unordered_map<node*, int> cnt;

 void traversal_trick(node *root)
{
    stack<node*> S;

    S.push(root);
    while(!S.empty())
    {
        node* cur = S.top();
        if(cur == NULL)
        {
        	S.pop();
        	continue;
        }
        if (cnt[cur] == 0)
        	S.push(cur->left);
        else if (cnt[cur] == 1)
        	cout << cur->val << " " ;
        else if (cnt[cur] == 2)
        	S.push(cur->right);
        else
        	S.pop();
        cnt[cur]++;
    }
}

##PreOrder

unordered_map<node*, int> cnt;

void traversal_trick(node *root)
{
    stack<node*> S;

    S.push(root);
    while(!S.empty())
    {
        node* cur = S.top();
        if(cur == NULL)
        {
        	S.pop();
        	continue;
        }
        if (cnt[cur] == 0)
        	cout << cur->val << " " ;
        else if (cnt[cur] == 1)
        	S.push(cur->left);
        else if (cnt[cur] == 2)
        	S.push(cur->right);
        else
        	S.pop();
        cnt[cur]++;
    }
}

##PostOrder

unordered_map<node*, int> cnt;

void traversal_trick(node *root)
{
    stack<node*> S;

    S.push(root);
    while(!S.empty())
    {
        node* cur = S.top();
        if(cur == NULL)
        {
        	S.pop();
        	continue;
        }
        if (cnt[cur] == 0)
        	S.push(cur->left);
        else if (cnt[cur] == 1)
        	S.push(cur->right);
        else if (cnt[cur] == 2)
        	cout << cur->val << " " ;
        else
        	S.pop();
        cnt[cur]++;
    }
}