Re: [閒聊] 每日LeetCode
https://leetcode.com/problems/minimum-depth-of-binary-tree/description/
111. Minimum Depth of Binary Tree
給你一個二元樹，返回他的最小深度，最小深度為 root 節點到葉子節點的最小距離。
Example 1:
https://assets.leetcode.com/uploads/2020/10/12/ex_depth.jpg
Input: root = [3,9,20,null,null,15,7]
Output: 2
Example 2:
Input: root = [2,null,3,null,4,null,5,null,6]
Output: 5
思路：
1.用廣度優先去traversal二元樹，如果某個節點的左右兩個子節點都為空，表示找到
最小深度。
Java Code：
-------------------------------------------
class Solution {
public int minDepth(TreeNode root) {
int depth = 0;
if (root == null) {
return depth;
}
Queue<TreeNode> queue = new LinkedList<>();
queue.offer(root);
while (!queue.isEmpty()) {
int size = queue.size();
depth++;
for (int i = 0; i < size; i++) {
TreeNode curr = queue.poll();
if (curr.left == null && curr.right == null) {
return depth;
}
if (curr.left != null) {
queue.offer(curr.left);
}
if (curr.right != null) {
queue.offer(curr.right);
}
}
}
return depth;
}
}
-------------------------------------------
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https://i.imgur.com/YPBHGGE.jpg
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