Day 14 (November 28, 2022)

Problem 19: 136. Single Number

Accepted

Problem 18: 190. Reverse Bits

Accepted

• Approach: Convert the number to bits by dividing by 2 until 0, storing the bits into an array. Then walk through the array backward and calculate the decimal representation.

Day 13 (November 26, 2022)

Problem 17: 191. Number of 1 Bits

Accepted

Problem 16: 231. Power of Two

Accepted

Day 12 (November 25, 2022)

Problem 15: 120. Triangle

Accepted

• DP approach. Overview: create a minimum path sum triangle array. Update from the bottom of the triangle
  • for each index i on kth row, the minimum path sum would be the minimum betw
    • triangle[k][i] + minPathSum[k+1][i]
    • triangle[k][i] + minPathSum[k+1][i+1]

Day 11 (November 24, 2022)

Problem 14: 784. Letter Case Permutation

Accepted

• Backtrack approach
  • Walk through all characters
    • if it’s a digit, concatenate the digit to current permutation
    • if it’s a letter, create two permutations:
      • concatenate the lowercased letter to current permutation
      • concatenate the uppercased letter to current permutation
    • Stop when number of characters is equal to original string. Return the permutation

Day 11 (November 23, 2022)