Given an integer matrix, find the length of the longest increasing path. From each cell, you can either move to four directions: left, right, up or down. You may NOT move diagonally or move outside of the boundary (i.e. wrap-around is not allowed). Example 1: Input: nums = [ [9,9,4],...
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## 129. Sum Root to Leaf Numbers

Given a binary tree containing digits from 0-9 only, each root-to-leaf path could represent a number.
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## 124. Binary Tree Maximum Path Sum

### Hard

Given a non-empty binary tree, find the maximum path sum.
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## 117. Populating Next Right Pointers in Each Node II

### Medium

Given a binary tree
struct Node {
int val;
Node *left;
Node *right;
Node *next;
}
Populate each next pointer to point to its next right node. If there is no next right node, the next pointer should be set to NULL.
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## 116. Populating Next Right Pointers in Each Node

### Medium

You are given a perfect binary tree where all leaves are on the same level, and every parent has two children. The binary tree has the following definition:
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## 114. Flatten Binary Tree to Linked List

### Medium

Given a binary tree, flatten it to a linked list in-place.
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