代码随想录第十六天: 二叉树part03

力扣222 完全二叉树的节点个数

class Solution {
    public int countNodes(TreeNode root) {
        if(root == null) return 0;
        TreeNode leftnode = root.left;
        int leftdepth = 0;
        TreeNode rightnode = root.right;
        int rightdepth = 0;
        while(leftnode != null) {
            leftnode = leftnode.left;
            leftdepth++;
        }
        while(rightnode != null) {
            rightnode = rightnode.right;
            rightdepth++;
        }
        if(rightdepth == leftdepth) return (2 << rightdepth) - 1;
        else {
            int leftnum = countNodes(root.left);
            int rightnum = countNodes(root.right);
            return 1 + leftnum + rightnum;
        }
    }
}

力扣111 二叉树的最小深度

class Solution {
    public int minDepth(TreeNode root) {
        if(root == null) return 0;
        int leftdepth = minDepth(root.left);
        int rightdepth = minDepth(root.right);
        if(root.left == null && root.right != null) return 1 + rightdepth;
        else if(root.left != null && root.right == null) return 1 + leftdepth;
        else if(root.left == null && root.right == null) return 1;
        else return 1 + Math.min(leftdepth, rightdepth);
    }
}

力扣104 二叉树的最大深度

class Solution {
    public int maxDepth(TreeNode root) {
        if(root == null) return 0;
        int leftheight = maxDepth(root.left);
        int rightheight = maxDepth(root.right);
        int height = 1 + Math.max(leftheight, rightheight);
        return height;
    }
}