> For the complete documentation index, see [llms.txt](https://a.b.cr/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://a.b.cr/dictionary/algorithm/diary/2022/06/2022-06-27.md).

# 2022-06-27

## [112. Path Sum](https://leetcode.com/problems/path-sum/)

### Description

Given the `root` of a binary tree and an integer `targetSum`, return `true` if the tree has a **root-to-leaf** path such that adding up all the values along the path equals `targetSum`.

A **leaf** is a node with no children.

**Example 1:**

![](https://img.content.cc/a/2022/06/27/11-13-10-134-742c651c576f3ecd182f1ad76ef48299-d4ba03.png)

```
Input: root = [5,4,8,11,null,13,4,7,2,null,null,null,1], targetSum = 22
Output: true
Explanation: The root-to-leaf path with the target sum is shown.
```

**Example 2:**

![](https://img.content.cc/a/2022/06/27/11-13-20-136-9e59eea0963a921ebdc0f48f2e375e29-46f9d3.png)

```
Input: root = [1,2,3], targetSum = 5
Output: false
Explanation: There two root-to-leaf paths in the tree:
(1 --> 2): The sum is 3.
(1 --> 3): The sum is 4.
There is no root-to-leaf path with sum = 5.
```

**Example 3:**

```
Input: root = [], targetSum = 0
Output: false
Explanation: Since the tree is empty, there are no root-to-leaf paths.
```

**Constraints:**

* The number of nodes in the tree is in the range `[0, 5000]`.
* `-1000 <= Node.val <= 1000`
* `-1000 <= targetSum <= 1000`

### Solution

#### Approach #0: DFS

```go
/**
 * Definition for a binary tree node.
 * type TreeNode struct {
 *     Val int
 *     Left *TreeNode
 *     Right *TreeNode
 * }
 */
func hasPathSum(root *TreeNode, targetSum int) bool {
    if root == nil {
        return false
    }
    if root.Left == nil && root.Right == nil {
        return root.Val == targetSum
    }
    return hasPathSum(root.Left, targetSum-root.Val) || hasPathSum(root.Right, targetSum-root.Val)
}
```

#### Approach #1: BFS

```go
/**
 * Definition for a binary tree node.
 * type TreeNode struct {
 *     Val int
 *     Left *TreeNode
 *     Right *TreeNode
 * }
 */
func hasPathSum(root *TreeNode, targetSum int) bool {
    if root == nil {
        return false
    }
    nodeQ := []*TreeNode{root}
    valQ := []int{0}
    for len(nodeQ) > 0 {
        node := nodeQ[0]
        nodeQ = nodeQ[1:]
        val := valQ[0]
        valQ = valQ[1:]
        if node.Left == nil && node.Right == nil && val+node.Val == targetSum {
            return true
        }
        if node.Left != nil {
            nodeQ = append(nodeQ, node.Left)
            valQ = append(valQ, node.Val+val)
        }
        if node.Right != nil {
            nodeQ = append(nodeQ, node.Right)
            valQ = append(valQ, node.Val+val)
        }
    }
    return false
}
```


---

# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.

## Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter:

```
GET https://a.b.cr/dictionary/algorithm/diary/2022/06/2022-06-27.md?ask=<question>&goal=<endgoal>
```

`ask` is the immediate question: it should be specific, self-contained, and written in natural language.
`goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal.

The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.