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April

Goal​

  1. Recursion
  2. Bit Manipulation
    1. 14 March, 2026 ✔
    2. 19 March, 2026 ✔
  3. Sliding Window
    1. 06 April, 2026 ✔
  4. Array
  5. 900 Rating: 50
  6. 1000 Rating: 50

Week 01​

05 April, 2026​

  1. https://codeforces.com/contest/2195/problem/A
    1. 17 March, 2026: 00.25.19 ❌
      • Failed at edge case
        • When you select elements, the product is defined as:
          • If you pick multiple numbers → multiply them all
          • If you pick one number → the product is just that number itself
  2. https://leetcode.com/problems/merge-close-characters/
    1. 05 April, 2026: 00.44.24 ❌
      • Intitution was right
        • You can erase string
        • Make sure the index are organize, not messy
  3. https://leetcode.com/problems/minimum-operations-to-make-array-parity-alternating/
    1. 05 April, 2026: 00.43.25 ❌
      • Intitution was right
      • Follow parity counting approach

06 April, 2026​

  • Task/Note 3

07 April, 2026​

  • Task/Note 3

08 April, 2026​

  • Task/Note 3

09 April, 2026​

  • Task/Note 3

10 April, 2026​

  • Task/Note 3

11 April, 2026​

  • Task/Note 3

Week 02​

12 April, 2026​

13 April, 2026​

  1. https://leetcode.com/problems/spiral-matrix-ii/
    1. 13 April, 2026: 00.07.53 ✔
  2. https://leetcode.com/problems/remove-duplicates-from-sorted-array-ii
    1. 13 April, 2026: 00.32.39 ✔
      • Count based approach
      • Regular approach: instead of last item, check last 2 item.
  3. https://leetcode.com/problems/container-with-most-water
    1. 13 April, 2026: 00.15.55 ❌
      • Failed at optimization
        • Implment bruteforce first
        • Think what technique can be used to reduce the polynomial complexity into linear complexity.
  4. https://leetcode.com/problems/4sum-ii/submissions/1977429910/
    1. 13 April, 2026: 00.14.58 ❌
      • Failed at optimization
        • Reduce the time complexity from n4n^4 to O(n1∗n2+n3∗n4)O(n1*n2 + n3*n4)

14 April, 2026​

  1. https://leetcode.com/problems/find-the-duplicate-number
    1. 14 April, 2026: 00.07.18 ❌
      • Failed at optimization
        • Instead of seeing nums as just an array, interpret it like this:
        • Each index = a node
        • Each value = pointer to next node
        • Since duplicate exists → cycle forms

15 April, 2026​

16 April, 2026​

17 April, 2026​

18 April, 2026​

Week 03​

19 April, 2026​

20 April, 2026​

  1. https://leetcode.com/problems/second-largest-digit-in-a-string
    1. 20 April, 2026: 00.05.58 ❌
      • Failed at optimization
        • Try to solve it within O(1)O(1) time complexity

21 April, 2026​

22 April, 2026​

23 April, 2026​

  1. https://leetcode.com/problems/reverse-linked-list-ii/
    1. 23 April, 2026: 00.10.51 ✔
  2. https://leetcode.com/problems/swap-nodes-in-pairs/
    1. 23 April, 2026: 00.12.16 ✔
  3. https://leetcode.com/problems/two-sum-ii-input-array-is-sorted/
    1. 23 April, 2026: 00.03.32 ✔

24 April, 2026​

25 April, 2026​

  1. https://leetcode.com/problems/next-greater-node-in-linked-list/description/
    1. 25 April, 2026: 00.04.06 ✔
  2. https://leetcode.com/problems/base-7/
    1. 25 April, 2026: 00.07.21 ✔
      • Failed at edge cases
        • Check if number is 0
        • 0 and "0" have different type
  3. https://leetcode.com/problems/add-two-numbers-ii
    1. 25 April, 2026: 00.06.44 ✔

Week 04​

26 April, 2026​

  1. https://leetcode.com/problems/largest-number
    1. 26 April, 2026: 00.09.47 ❌
      • Failed at edge case
        • Sort the array length wise, not value wise
        • Handle the front 0 case
        • to_string() convert an integer to string
        • stoll() convert an string to integer
  2. https://leetcode.com/problems/intersection-of-two-arrays
    1. 26 April, 2026: 00.08.58 ✔
      • Solve in every possible way.
  3. https://leetcode.com/problems/reverse-linked-list-ii
    1. 26 April, 2026: 00.07.12 ✔
      • Assign both newCurrent->next and newCurrent for creating new list
  4. https://leetcode.com/problems/double-a-number-represented-as-a-linked-list
    1. 26 April, 2026: 00.07.15 ✔
      • Try to optmize it more(instead of O(3n),canyousolveitwithO(3n), can you solve it with O(n)$)
  5. https://leetcode.com/problems/delete-nodes-from-linked-list-present-in-array
    1. 26 April, 2026: 00.09.24 ✔
  6. https://leetcode.com/problems/smallest-value-of-the-rearranged-number/
    1. 26 April, 2026: 00.07.59 ✔
  7. https://leetcode.com/problems/product-of-array-except-self
    1. 26 April, 2026: 00.08.44 ✔

27 April, 2026​

  1. https://leetcode.com/problems/find-all-duplicates-in-an-array
    1. 27 April, 2026: 00.12.25 ❌
      • Failed at optimization
        • Solve it within O(n)O(n) time complexity
        • Hints 1: there must 1 small element present in the array, except one
        • Hints 2: mark/replace the visited item as -1

28 April, 2026​

29 April, 2026​

30 April, 2026​

  1. https://leetcode.com/problems/count-primes/
    1. 30 April, 2026: 00.15.10 ❌
      • Failed at edge cases
        • Approach was right
        • Check how many time outer loop need to run
        • Check when inner loop begins its execution
        • Check how many step inner loop move in each step
  2. https://leetcode.com/problems/factorial-trailing-zeroes/
    1. 30 April, 2026: 00.15.10 ❌
      • Failed at edge cases
        • Approach was right divide with correct number
  3. https://leetcode.com/problems/trim-trailing-vowels/
    1. 30 April, 2026: 00.01.24 ✔
      • A trailing vowel is any character in u that appears at the end of the string.

01 May, 2026​

  1. https://leetcode.com/problems/first-bad-version/
    1. 01 May, 2026: 00.01.22 ✔
  2. https://leetcode.com/problems/find-target-indices-after-sorting-array/
    1. 30 April, 2026: 00.01.24 ❌
      • Failed at optimization
        • Try to solve it within O(n)O(n) time complexity

02 May, 2026​