1325-delete-leaves-with-a-given-value.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)
 * }
 */
/**
 * DFS | PostOrder traversal
 * Time O(n) | Space O(n)
 * https://leetcode.com/problems/delete-leaves-with-a-given-value
 * @param {TreeNode} root
 * @param {number} target
 * @return {TreeNode}
 */
var removeLeafNodes = function(root, target) {
    
    const dfs = (node) => {
        if (!node) return null;
        node.left = dfs(node.left);
        node.right = dfs(node.right);
        if (!node.left && !node.right) {
            if (node.val === target) return null;
        }
        return node;
    }

    return dfs(root);
};