#0276

Path Sum

EasyDSA18 min10 XP

Problem

A tree node is [value, left, right]. Return True if any root-to-leaf path has values summing to target.

Why This Matters

Path Sum teaches how recursive state changes as you move down a tree.

Function Signature

def has_path_sum(root, target):

Examples

Example 1

Inputroot = [5,[4,None,None],[8,[13,None,None],[4,None,[1,None,None]]]], target = 18

OutputTrue

The path 5 -> 8 -> 4 -> 1 sums to 18.

Constraints

Return the exact requested value.
Handle edge cases cleanly.
Use the intended DSA pattern when brute force would scale poorly.

CodePython

def has_path_sum(root, target):
    """
    Input example: root = [5,[4,None,None],[8,[13,None,None],[4,None,[1,None,None]]]], target = 18
    Return: True
    Return the value from the function so the tests can compare it. Do not print unless the prompt asks.
    """
    # write your code here
    return False

def has_path_sum(root, target):
    """
    Input example: root = [5,[4,None,None],[8,[13,None,None],[4,None,[1,None,None]]]], target = 18
    Return: True
    Return the value from the function so the tests can compare it. Do not print unless the prompt asks.
    """
    # write your code here
    return False

Visible browser tests run here when available.

Testcases2 visible / 3 hidden categories

Path exists

Inputtarget 18

ExpectedTrue

One root-to-leaf path hits the target.

No root-to-leaf path

Input[1, [2], [3]], target 5

ExpectedFalse

1 + 3 is 4, and 1 + 2 is 3.

Hidden Test Categories

negative valuessingle node equals targettarget only appears on non-leaf prefix