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. 递归的解题思路: 递归当前结点,分一下四种情况考虑:①结点为空时返回0:②结点没有右子树时,返回左子树最小值+1:③结点没有左子树时,返回右子树最小值+1:④当结点双子齐全时,返回…