Leetcode 814 二叉树剪枝

　　JAVA：

   public final TreeNode pruneTree(TreeNode root) {
        if(!hasOne(root)) return null;
        return root;
    }

    private final boolean hasOne(TreeNode node) {
        if (node == null) return false;
        boolean left = hasOne(node.left), right = hasOne(node.right);
        if (!left) node.left = null;
        if (!right) node.right = null;
        return left || right || node.val == 1;
    }

　　JS:

/**
 * 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 {TreeNode}
 */
var pruneTree = function (root) {
    if (!hasOne(root)) return null;
    return root;
};

var hasOne = (node) => {
    if (!node) return false;
    let left = hasOne(node.left), right = hasOne(node.right);
    if (!left) node.left = null;
    if (!right) node.right = null;
    return left || right || node.val == 1;
}