965. 单值二叉树

965. 单值二叉树

type TreeNode struct {
    Val   int
    Left  *TreeNode
    Right *TreeNode
}
func isUnivalTree(root *TreeNode) bool {
    if root == nil {
        return true
    }
    stack := []*TreeNode{root}
    var v = root.Val
    for len(stack) > 0 {
        size := len(stack)
        for i := 0; i < size; i++ {
            node := stack[i]
            if node.Val != v {
                return false
            }
            if node.Left != nil {
                stack = append(stack, node.Left)
            }
            if node.Right != nil {
                stack = append(stack, node.Right)
            }
        }
        stack = stack[size:]
    }
    return true

递归

func isUnivalTree1(root *TreeNode) bool {
    if root == nil {
        return true
    }
    if root.Left != nil && root.Val != root.Left.Val {
        return false
    }
    if root.Right != nil && root.Val != root.Right.Val {
        return false
    }
    return isUnivalTree(root.Left) && isUnivalTree(root.Right)
}