문제Given 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. 입력root = [3,9,20,null,null,15,7] 출력2 제한The number of nodes in the tree is in the range [0, 105].-1000 풀이1 (js)/** * Definition for a binary tree node. * function TreeNode(val, left, right) { * ..