20220517

合并二叉树

输入：{1,3,2,5},{2,1,3,#,4,#,7}
返回值：{3,4,5,5,4,#,7}

解题思路：
同时递归两棵树；
考虑到节点有以下情况
t1 = null, t2!=null      val = t1
t1 != null, t2=null      val = t2
t1 = null, t2 = null     val = t2(0)
t1 != null, t2 !=null    val = t1+t2
function mergeTrees( t1 ,  t2 ) {
    // write code here
    const dfs = (node1, node2) => {
        if(node1==null) return node2
        if(node2==null) return node1
        node1.val += node2.val
        node1.left = dfs(node1.left, node2.left)
        node1.right = dfs(node1.right, node2.right)
        return node1
    }
    return dfs(t1, t2)
}

二叉树的镜像

输入：{8,6,10,5,7,9,11}

返回值：{8,10,6,11,9,7,5}

解题思路：左右互换 + 递归
function Mirror( pRoot ) {
    // write code here
    const dfs = (node)=> {
        if(!node) return
        let temp = node.left
        node.left = node.right
        node.right = temp
        dfs(node.left)
        dfs(node.right)
        return node
    }
    return dfs(pRoot)
}