Poison

111. Minimum Depth of Binary Tree

发表于
DFS
1
2
3
4
5
6
7
8
9
10
11
12
13
class Solution {
    public int minDepth(TreeNode root) {
        if (root == null) {
            return 0;
        } else if (root.left == null) {
            return minDepth(root.right) + 1;
        } else if (root.right == null) {
            return minDepth(root.left) + 1;
        } else {
            return Math.min(minDepth(root.left), minDepth(root.right)) + 1;
        }
    }
}
BFS
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
class Solution {
    public int minDepth(TreeNode root) {
        int depth = 0;

        Queue<TreeNode> queue = new LinkedList<>();
        if (root != null) {
            queue.add(root);
        }

        while (!queue.isEmpty()) {
            for (int i = queue.size(); i > 0; i--) {
                TreeNode node = queue.poll();
                if (node.left == null && node.right == null) {
                    return depth + 1;
                }
                if (node.left != null) {
                    queue.add(node.left);
                }
                if (node.right != null) {
                    queue.add(node.right);
                }
            }

            depth++;
        }

        return depth;
    }
}
Reference

111. Minimum Depth of Binary Tree