leetcode 652. Find Duplicate Subtrees Map记录查询 + 深度优先遍历DFS
Givenabinarytree,returnallduplicatesubtrees.Foreachkindofduplicatesubtrees,youonlyneedtoreturntherootnodeofanyoneofthem.Twotreesareduplicateiftheyhavethesamestructurewithsamenodevalues.Example1:1/\23/