111. Minimum Depth of Binary Tree

最新推荐文章于 2023-12-15 03:22:29 发布

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最新推荐文章于 2023-12-15 03:22:29 发布

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分类专栏： Leetcode Algorithm JAVA

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本文介绍了一种寻找二叉树最小深度的算法，通过广度优先搜索（BFS）策略，从根节点开始，逐层遍历直至找到最近的叶子节点，返回其路径上的节点数作为最小深度。

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Given a binary tree, find its minimum depth.

The minimum depth is the number of nodes along the shortest path from the root node down to the nearest leaf node.

Note: A leaf is a node with no children.

Example:

Given binary tree [3,9,20,null,null,15,7],

return its minimum depth = 2.

class Solution {
    public int minDepth(TreeNode root) {
        int c = 1;
        TreeNode tmp;
        Queue<TreeNode> Q = new LinkedList<> ();
        
        if (root ==  null) return 0;
        
        Q.offer(root);
        Q.offer(null);
        while (!Q.isEmpty()) {
            tmp = Q.poll();
            if (tmp != null) {
                
                if (tmp.left == null && root.right == null) {
                    System.out.println("root value is " + root.val );
                    break;
                }  <====这里没有执行！！！！！！！！！！！！！
                
                if (tmp.left != null) {
                    Q.offer(tmp.left);
                    System.out.println("cl is " + c);
                } else {
                    System.out.println("left is null,c is " + c);
               
                }
                                
                if (tmp.right != null) {
                    Q.offer(tmp.right);
                    System.out.println("cr is " + c);
                }  
            }
            if (tmp == null) {
                
                if (!Q.isEmpty()) {
                    Q.offer(null);
                    c++;
                }
            }                    
        } 
        return c ;
    }
}