Leetcode
Tree
Depth-first Search
Breadth-first Search
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], 3 / 9 20 / 15 7 return its minimum depth = 2.
分析¶
DFS版本的递归:
public int minDepth(TreeNode root) { if(root == null) return 0; int left = minDepth(root.left); int right = minDepth(root.right); return (left == 0 || right == 0) ? left + right + 1: Math.min(left, right) + 1; }
最关键在于判断左子树和右子树存在的情况,并区别对待。
类似题目: Q104. Maximum Depth of Binary Tree
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