LeetCode/103. Binary Tree Zigzag Level Order Traversal at main · raiden-02/LeetCode · 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
/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
 * };
 */
class Solution {
public:
    vector<vector<int>> zigzagLevelOrder(TreeNode* root) {
        if(!root)
            return {};

        vector<vector<int>> ans;
        queue<TreeNode*> q;
        q.push(root);
        int sw = 0;

        while(!q.empty()) {
            int s = q.size();
            vector<int> tmp;
            while(s--) {
                TreeNode* cur = q.front(); q.pop();
                tmp.push_back(cur->val);

                if(cur->left)
                    q.push(cur->left);

                if(cur->right)
                    q.push(cur->right);
            }
            if(sw)
                reverse(tmp.begin(), tmp.end());
            ans.push_back(tmp);
            sw = (sw + 1) % 2;
        }

        return ans;
    }
};

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
 * };
 */
class Solution {
public:
    vector<vector<int>> zigzagLevelOrder(TreeNode* root) {
        if(not root)
            return {};

        queue<TreeNode*> q;
        q.push(root);
        int sw = 0;
        vector<vector<int>> ans;

        while(not q.empty()) {
            int s = q.size();
            vector<int> tmp;

            while(s--) {
                TreeNode* cur = q.front(); q.pop();

                if(sw % 2)
                    tmp.insert(tmp.begin(), cur->val);

                else
                    tmp.push_back(cur->val);

                if(cur->left)
                    q.push(cur->left);

                if(cur->right)
                    q.push(cur->right);
            }

            sw++;
            ans.push_back(tmp);
        }

        return ans;
    }
};