solution.js

/**
 * Definition for a binary tree node.
 * function TreeNode(val) {
 *     this.val = val;
 *     this.left = this.right = null;
 * }
 */
/**
 * @param {TreeNode} root
 * @param {number} sum
 * @return {number[][]}
 */
// DFS 有点回溯类问题的味道
var pathSum = function (root, sum) {
    if (!root) {
        return [];
    }
    const sequences = [];
    function helper (node, arr, cur) {
        // leaf node
        if (!node.left && !node.right) {
            if (node.val + cur === sum) {
                arr.push(node.val);
                sequences.push(arr);
            }
            return;
        }
        if (!node.left) {
            arr.push(node.val);
            return helper(node.right, arr, cur + node.val);
        }
        if (!node.right) {
            arr.push(node.val);
            return helper(node.left, arr, cur + node.val);
        }
        helper(node.left, arr.concat(node.val), cur + node.val);
        helper(node.right, arr.concat(node.val), cur + node.val);
    }
    helper(root, [], 0);
    return sequences;
};