LC 74

Question 1

Two Sums
Input: nums = [2,7,11,15], target = 9
Output: [0,1]
Explanation: Because nums[0] + nums[1] == 9, we return [0, 1].

Answer 1

use hashmap

Question 2

Longest Substring Without Repeating Characters
Input: s = “abcabcbb”
Output: 3
Explanation: The answer is “abc”, with the length of 3.

Answer 2

???

Question 3

Longest Palindromic Substring
Input: s = “babad”
Output: “bab”
Explanation: “aba” is also a valid answer.

Answer 3

???

Question 4

Container With Most Water
Input: height = [1,8,6,2,5,4,8,3,7]
Output: 49
Explanation: The above vertical lines are represented by array [1,8,6,2,5,4,8,3,7]. In this case, the max area of water (blue section) the container can contain is 49.

Answer 4

find max area by multiplying

min height between arr[x] or arr[y] * (y-x)

Question 5

3Sums

Answer 5

sort the array 
use 2sums and add logic 
2sums + arr[x]   > 0 
     reduce end 
2sums + arr[x] < 0 
      increment start 
else
      you found 3 elements adds to 0

Question 6

Remove Nth Node From End of List
Input: head = [1,2,3,4,5], n = 2
Output: [1,2,3,5]

Answer 6

use temp node to point to head and keep traversing
while this keep counter
counter reaches the n the node
set the temp.next to next of next

Question 7

Valid Parentheses

Question 8

Merge Two Sorted Lists
Input: list1 = [1,2,4], list2 = [1,3,4]
Output: [1,1,2,3,4,4]
ListNode

Question 9

Search in Rotated Sorted Array

Question 10

Rotate Image

Question 11

Group Anagrams

Question 12

Maximum Subarray
Input: nums = [-2,1,-3,4,-1,2,1,-5,4]
Output: 6
Explanation: [4,-1,2,1] has the largest sum = 6.

Answer 12

find max
keep calculating temp max
max is max, tempmax

Question 13

Spiral Matrix

Question 14

Jump Game

Question 15

Merge Intervals

Question 16

Merge k Sorted Lists
Input: lists = [[1,4,5],[1,3,4],[2,6]]
Output: [1,1,2,3,4,4,5,6]
Explanation: The linked-lists are:
[
  1->4->5,
  1->3->4,
  2->6
]
merging them into one sorted list:
1->1->2->3->4->4->5->6

Question 17

Insert Interval

Question 18

Unique Paths

Question 19

Climbing Stairs
Input: n = 2
Output: 2
Explanation: There are two ways to climb to the top.
1. 1 step + 1 step
2. 2 steps

Question 20

Set Matrix Zeroes

Question 21

Minimum Window Substring

Question 22

Word Search

Question 23

Decode Ways

Question 24

Validate Binary Search Tree

Question 25

Same Tree