Code Templates

Problems

• Two Sum
• Median of two sorted arrays
• container with most water
• 3Sum
• 3Sum Closest
• 4Sum
• Remove Duplicates from Sorted Array
• Remove Element
• Next Permutation
• Search in Rotated Sorted Array
• Find first and last position of element in sorted array
• search insert position
• combination sum
• combination sum II
• first missing positive
• trappint rain water
• jump game II
• rotate image
• maximum subarray
• spiral matrix
• jump game
• merge intervals
• insert interval
• spiral matrix II
• unique paths
• unique paths II
• minimum path sum
• plus one
• set matrix zeroes
• search a 2D matrix
• sort colors
• subsets
• word search
• remove duplicates from sorted array II
• largest rectangle in histogram
• merge sorted array
• subsets II
• construct binary tree from preorder and inorder Traversal
• construct binary tree from Inorder and Postorder Traversal
• pscal’s triangle
• pasal’s triangle II
• Triangle
• best time to buy and sell stock
• best time to buy and sell stock II
• word ladder II
• longest consecutive sequence
• maximum product subarray
• find minimum in rotated sorted array
• find minimum in rotated sorted array II
• find peak element
• two sum - input array is sorted
• majority element
• rotate array
• minimum size subarray sum
• combination sum III
• contains duplicate
• contains duplicate II
• summary ranges
• majority element II
• missing number
• move zeroes
• find the duplicate number
• third maximum number
• find all numbers disppeared in an array
• circular array loop
• max consecutive ones
• fibonacci number
• k-diff pairs in an array
• array partition I
• reshape the matrix
• shortest unsorted continuous subarray
• can place flowers
• maximum product of three times
• maximum product of three numbers
• maximum average subarray I
• image smoother
• non-decreasing array
• beautiful arrangement II
• longest continuous increasing subsequence
• max area of island
• degree of an array
• subarray product less than K
• best time to buy and sell stock with transaction fee
• 1-bit and 2bit characters
• maximum length of repeated subarray
• find pivot index
• my calendar I
• min cost climbing stairs
• toeplitz matrix
• global and local inversions
• number of subarrarys with bounded maximum
• positions of large groups
• flipping an image
• transpose matrix
• advantage shuffle
• fair candy swap
• sum of subsequence widths
• monotonic
• array
• sum of sumarray minimums
• x of a kind in a deck of cards
• maximum sum circular subarray
• sort array by parity II
• pancake sorting
• squares of a sorted array
• longest turbulent subarray
• sum of even numbers after queries
• add to array-form of integer
• available captures for rook
• find common characters
• capacity to ship packages within D days
• binary prefix divisible by 5
• moving stones until consecutive II
• height checker
• grumpy bookstore owner
• number of submatrices that sum to target
• duplicate zeros
• relative sort array
• number of equivalent domino pairs
• online majority element in subarray
• find words that can be formed by characters
• compare string by frequency of the smallest character
• distance between bus stops
• day of the week
• minimum absolute difference
• smallest string with swaps
• get equal substrings within budget
• minimum cost to move chips to the same position
• check if it is a straight line
• cells with oodd values in a matrix
• shift 2d grid
• minimum time visiting all points
• find winner on a tic tac toe game
• element appearing more then 25% in sorted array
• reaplace elements with greatest element on right side
• sum of mutated array closest to target
• find n unique integers sum up to zero
• decompress run-length encoded list
• sort the matrix diagonally
• the K weakest rows in a matrix
• lucky numbers in a matrix
• find the distance value between two arrays
• create target array in the given order
• maximum points you can obtain from cards
• check if all 1’s are at least length K places away
• longest continuous subarray with absolute diff less than or equal to limit
• count triplets that can form two arrays of equal XOR
• maximum product of two elements in an array
• maximum area of a piece of cake after horizontal and vertical cuts
• shuffle the array
• running sum of 1d array
• minimum number of days to make m bouquets
• XOR operations in an array
• number of good pairs
• kth missing positive number
• matrix diagonal sum
• special array with x elements greater than or equal x
• mean of array after removing some elements
• slowest key
• sort array by increasing frequency
• check array formation through concatenation
• get maximum in generated array
• defuse the bomb
• design an ordered stream
• richest customer wealth
• number of students unable to eat lunch
• find the highest altitude
• find kth largest xor corrdinate value
• maximum number of balls in a box
• sum of unique elements
• check if array is sorted and rotated
• minimum changes to make alternating binary string

two pointers

• longest substring without repeating characters
• container with most water
• 3Sum
• 3Sum Closest
• 4Sum
• remove Nth node from end of list
• remove duplicate from sorted array
• remove element
• implement strStr()
• substring with concatenation of all words
• trapping rain water
• rotate list
• sort colors
• minimum window substring
• remove duplicates from sorted array II
• partition list
• merge sorted array
• valid palindrome
• linked list cycle
• linked list cycle II
• longest substring with at most two distinct characters
• two sum II - input array is sorted
• minimum size subarray sum
• palindrome linked list
• 3Sum smaller
• move zeroes
• find the duplicate number
• reverse string
• reverse vowels of a string
• intersection of two arrays
• intersection of two arrays II
• sort transformed array
• longest repeating chracter replacement
• circular array loop
• max consecutive ones II
• longtest word in dictionary through deleting
• k-diff pairs in an array
• permutation in string
• smallest range covering elements from k lists
• subarray product less than k
• candy crush
• partition labels
• most profit assigning work
• unique letter string
• push dominoes
• backspace string compare
• longest mountain in array
• boats to save people
• fruit into baskets
• 3sum with multiplicity
• long pressed name
• binary subarrays with sum
• squares of a sorted array
• interval list intersections
• subarrays with k different integers
• max consecutive ones III
• statistics from a large sample
• replace the substring for balanced string
• minimum operations to reduce x to zero

Solutions

move zeroes

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class Solution:
  def move_zeroes(self, nums: List[int]) -> List[int]:
    j = 0
    for i in range(len(nums)):
      if nums[i] != 0:
        nums[i], nums[j] = nums[j], nums[i]
        j+=1
    return nums

container with most water

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class Solution:
  def container(self, nums: List[int]) -> int:
    n = len(nums)
    l, r = 0, n - 1
    max_ = 0
    while l < r:
      max_ = max(max_, (r-l)*min(nums[l], nums[r]))
      if nums[l] < nums[r]:
        l += 1
      else:
        r -= 1
    return max_

rotate array

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class Solution:
  def rotate(self, nums: List[int], k: int) -> None:
    """
    make an extra copy and then rotate
    """
    n = len(nums)
    cp = copy.deepcopy(nums)
    for i in range(n):
      nums[(i+k)%n] = cp[i]

  def rotate(self, nums: List[int], k: int) -> None:
    """
    Reverse the first n - k elements, the last k elements, and then all the n elements.
    """
    n = len(nums)
    k = k % n
    # reverse, inclusive
    def rev(nums, i, j):
      while i < j:
        nums[i], nums[j] = nums[j], nums[i]
        i+=1
        j-=1
    rev(nums, 0, n-1)
    rev(nums, 0, k-1)
    rev(nums, k, n-1)