222. Count Complete Tree Nodes

[Tcdian]

222. Count Complete Tree Nodes

给出一个 完全二叉树，求出该树的节点个数。

Note

完全二叉树的定义如下：在完全二叉树中，除了最底层节点可能没填满外，其余每层节点数都达到最大值，并且最下面一层的节点都集中在该层最左边的若干位置。若最底层为第 h 层，则该层包含 1~ 2^h 个节点。

Example

Input: 
    1
   / \
  2   3
 / \  /
4  5 6

Output: 6

[Tcdian]

Solution

• JavaScript Solution

/**
 * Definition for a binary tree node.
 * function TreeNode(val, left, right) {
 *     this.val = (val===undefined ? 0 : val)
 *     this.left = (left===undefined ? null : left)
 *     this.right = (right===undefined ? null : right)
 * }
 */
/**
 * @param {TreeNode} root
 * @return {number}
 */
var countNodes = function(root) {
    if (root === null) {
        return 0;
    }
    const leftDepth = countDepth(root.left);
    const rightDepth = countDepth(root.right);
    if (leftDepth === rightDepth) {
        return 1 + countNodes(root.right) + (1 << leftDepth) - 1;
    } else {
        return 1 + countNodes(root.left) + (1 << rightDepth) - 1;
    }
};

function countDepth(patrol) {
    let depth = 0;
    while(patrol !== null) {
        depth++;
        patrol = patrol.left;
    }
    return depth;
}

• TypeScript Solution

/**
 * Definition for a binary tree node.
 * class TreeNode {
 *     val: number
 *     left: TreeNode | null
 *     right: TreeNode | null
 *     constructor(val?: number, left?: TreeNode | null, right?: TreeNode | null) {
 *         this.val = (val===undefined ? 0 : val)
 *         this.left = (left===undefined ? null : left)
 *         this.right = (right===undefined ? null : right)
 *     }
 * }
 */

function countNodes(root: TreeNode | null): number {
    if (root === null) {
        return 0;
    }
    const leftDepth = countDepth(root.left);
    const rightDepth = countDepth(root.right);
    if (leftDepth === rightDepth) {
        return 1 + countNodes(root.right) + (1 << leftDepth) - 1;
    } else {
        return 1 + countNodes(root.left) + (1 << rightDepth) - 1;
    }
};

function countDepth(patrol: TreeNode | null): number {
    let depth = 0;
    while(patrol !== null) {
        depth++;
        patrol = patrol.left;
    }
    return depth;
}