112. 路径总和🔖DFS

/**
 * 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
 * @param {number} targetSum
 * @return {boolean}
 */
var hasPathSum = function(root, targetSum) {
    let result = false
    let dfs = (data, presum, tar) => {
        if (data) {
            presum = data.val + presum
            if (!data.left && !data.right) {
                if (presum == tar) {
                    result = true
                }
            }
            dfs(data.left, presum, tar)
            dfs(data.right, presum, tar)
        }
    }
    dfs(root, 0, targetSum)
    return result
};