LeetCode 743. Network Delay Time

ID	Title	Difficulty
1	Two Sum	Easy
2	Add Two Numbers	Medium
3	Longest Substring Without Repeating Characters	Medium
4	Median of Two Sorted Arrays	Hard
5	Longest Palindromic Substring	Medium
6	Zigzag Conversion	Medium
7	Reverse Integer	Medium
8	String to Integer (atoi)	Medium
9	Palindrome Number	Easy
10	Regular Expression Matching	Hard
11	Container With Most Water	Medium
12	Integer to Roman	Medium
13	Roman to Integer	Easy
14	Longest Common Prefix	Easy
15	3Sum	Medium
16	3Sum Closest	Medium
17	Letter Combinations of a Phone Number	Medium
18	4Sum	Medium
19	Remove Nth Node From End of List	Medium
20	Valid Parentheses	Easy
21	Merge Two Sorted Lists	Easy
22	Generate Parentheses	Medium
23	Merge k Sorted Lists	Hard
24	Swap Nodes in Pairs	Medium
25	Reverse Nodes in k-Group	Hard
26	Remove Duplicates from Sorted Array	Easy
27	Remove Element	Easy
28	Find the Index of the First Occurrence in a String	Easy
29	Divide Two Integers	Medium
30	Substring with Concatenation of All Words	Hard
31	Next Permutation	Medium
32	Longest Valid Parentheses	Hard
33	Search in Rotated Sorted Array	Medium
34	Find First and Last Position of Element in Sorted Array	Medium
35	Search Insert Position	Easy
36	Valid Sudoku	Medium
37	Sudoku Solver	Hard
38	Count and Say	Medium
39	Combination Sum	Medium
40	Combination Sum II	Medium
41	First Missing Positive	Hard
42	Trapping Rain Water	Hard
43	Multiply Strings	Medium
44	Wildcard Matching	Hard
45	Jump Game II	Medium
46	Permutations	Medium
47	Permutations II	Medium
48	Rotate Image	Medium
49	Group Anagrams	Medium
50	Pow(x, n)	Medium

Title

Difficulty

Two Sum

Easy

Add Two Numbers

Medium

Longest Substring Without Repeating Characters

Medium

Median of Two Sorted Arrays

Hard

Longest Palindromic Substring

Medium

Zigzag Conversion

Medium

Reverse Integer

Medium

String to Integer (atoi)

Medium

Palindrome Number

Easy

Regular Expression Matching

Hard

Container With Most Water

Medium

Integer to Roman

Medium

Roman to Integer

Easy

Longest Common Prefix

Easy

3Sum

Medium

3Sum Closest

Medium

Letter Combinations of a Phone Number

Medium

4Sum

Medium

Remove Nth Node From End of List

Medium

Valid Parentheses

Easy

Merge Two Sorted Lists

Easy

Generate Parentheses

Medium

Merge k Sorted Lists

Hard

Swap Nodes in Pairs

Medium

Reverse Nodes in k-Group

Hard

Remove Duplicates from Sorted Array

Easy

Remove Element

Easy

Find the Index of the First Occurrence in a String

Easy

Divide Two Integers

Medium

Substring with Concatenation of All Words

Hard

Next Permutation

Medium

Longest Valid Parentheses

Hard

Search in Rotated Sorted Array

Medium

Find First and Last Position of Element in Sorted Array

Medium

Search Insert Position

Easy

Medium

Hard

Medium

Medium

Medium

First Missing Positive

Hard

Hard

Medium

Hard

Medium

Medium

Medium

Medium

Medium

Medium

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Problem

You are given a network of n nodes, labeled from 1 to n. You are also given times, a list of travel times as directed edges $t i m e s [i] = (u_{i}, v_{i}, w_{i})$ , where $u_{i}$ is the source node, $v_{i}$ is the target node, and $w_{i}$ is the time it takes for a signal to travel from source to target.

We will send a signal from a given node k. Return the minimum time it takes for all the n nodes to receive the signal. If it is impossible for all the n nodes to receive the signal, return -1.

Example 1:

Input: times = [[2,1,1],[2,3,1],[3,4,1]], n = 4, k = 2
Output: 2

Example 2:

Input: times = [[1,2,1]], n = 2, k = 1
Output: 1

Example 3:

Input: times = [[1,2,1]], n = 2, k = 2
Output: -1

Constraints:

1 <= k <= n <= 100
1 <= times.length <= 6000
times[i].length == 3
$1 <= u_{i}, v_{i} <= n$
$u_{i}! = v_{i}$
$0 <= w_{i} <= 100$
All the pairs $(u_{i}, v_{i})$ are unique. (i.e., no multiple edges.)