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Tracker2

CF Ladder​

  • 1000 - 1
  • 900 - 2
  • 800 - 1

Week 1​

23 February, 2026​

  1. https://codeforces.com/contest/2192/problem/B
    • There are total 4 possible combination, correct combination consider as false combination
  2. https://codeforces.com/contest/1878/problem/C
    • Not sum of [1, ..., n], consider sum of last k digit
  3. https://codeforces.com/contest/1878/problem/A
  4. https://codeforces.com/contest/1850/problem/D

24 February, 2026​

  1. https://codeforces.com/contest/1203/problem/C
    • List of common divisor shouldn't consider if i == gcd/i
  2. https://codeforces.com/contest/282/problem/A
  3. https://codeforces.com/contest/1475/problem/A
    • even - even = result_even
      even - odd = result_even
      here dividing result_even by 2 doesn't produce the odd one, divide the result even by 2^k/n & (n - 1)
  4. https://codeforces.com/contest/1617/problem/B
    • Approach was right but consider wrong(i, n-i) case instead (i, n-i-1) as another number is 1, it shouldn't be consider
    • order of printing matter
    • gcd checking should be begin with 2
  5. https://codeforces.com/problemset/problem/1462/C
  6. https://codeforces.com/contest/26/problem/A

25 February, 2026​

  1. https://codeforces.com/contest/2192/problem/A
    • Intitution was wrong
    • Frequency count fail for abab
    • Consider the last and first character
  2. https://codeforces.com/contest/2203/problem/A

26 February, 2026​

  1. https://codeforces.com/problemset/problem/1553/A
  2. https://codeforces.com/problemset/problem/1542/A

Week 2​

27 February, 2026​

  1. https://codeforces.com/problemset/problem/1535/B
    • Its not required to make the pair distinct
    • Array can be sort by even/odd with sort function
  2. https://codeforces.com/problemset/problem/1537/B
    • yo-yo can be thrown in the same place where Antos stand at
  3. https://codeforces.com/problemset/problem/1611/A
    • it ask how many prefix reversals needed
    • it doesn't ask the index from where it should be reversed so that the number is even
  4. https://leetcode.com/problems/sort-array-by-parity/description/
  5. https://leetcode.com/problems/odd-even-linked-list/
  6. https://leetcode.com/problems/find-numbers-with-even-number-of-digits/
  7. https://leetcode.com/problems/gcd-of-odd-and-even-sums/
    • Sum of first nth even number = n(n+1)
    • Sum of first nth odd number = n*n

28 February, 2026​

  1. https://codeforces.com/problemset/problem/1475/A
    • here dividing result_even by 2 doesn't produce the odd one, divide the result even by 2^k/n & (n - 1)
  2. https://codeforces.com/contest/1462/problem/C
  3. https://codeforces.com/problemset/problem/1374/B
    • Multiply by 2 means add one 2 from its prime factorizatoin.
    • Divide by 6 means remove one 2 and one 3 from its prime factorization.
    • Our end goal is to remove the factorization
    • We must perform all possible operation of removing/division, if we have shortage of 2, it can be filled my multiplying 2
  4. https://codeforces.com/problemset/problem/1475/B
    • n = 2020x + 2021y
    • n = 2020x + 2020y + y
    • n = 2020 (x + y) + y
    • n = 2020q + r - apply divisibility rule(r <= q)
  5. https://codeforces.com/contest/2200/problem/A
    • it ask how many time win, i thought who win
  6. https://codeforces.com/contest/2200/problem/B
    • for non-decresing order, the condition should be <= but i only use <
    • is_sorted is used to check wheather a iterator sorted or not
  7. https://codeforces.com/contest/2200/problem/C
    • approach was right, jsut couldn't able to impment it
    • why the outer loop need to iterate n/2 times?
      • each operation remove 2 pairs, so maximum possible deletion is(n/2) pairs
    • i < size - 1 can be replaced with i + 1 < size

01 March, 2026​

  1. https://codeforces.com/contest/2203/problem/B
    • Intitution was correct, just couldn't able to implement it
    • sort the digits, while extracting the digit consider all the same except the first one, reduce it by 1
  2. https://codeforces.com/problemset/problem/318/A
    • all are correct, just put the wrong condition

02 March, 2026​

03 March, 2026​

  1. https://www.geeksforgeeks.org/problems/find-pairs-with-given-sum-in-doubly-linked-list/1

05 March, 2026​

  1. https://leetcode.com/problems/add-two-numbers/
  2. https://leetcode.com/problems/roman-to-integer/
  3. https://www.geeksforgeeks.org/problems/add-1-to-a-number-represented-as-linked-list/1

06 March, 2026​

  1. https://leetcode.com/problems/maximum-twin-sum-of-a-linked-list/description/
  2. https://www.geeksforgeeks.org/problems/delete-all-occurrences-of-a-given-key-in-a-doubly-linked-list/1
  3. https://leetcode.com/problems/remove-duplicates-from-sorted-list

Week 3​

07 March, 2026​

08 March, 2026​

09 March, 2026​

  1. https://leetcode.com/problems/longest-harmonious-subsequence/
    • harmonious subsequence doesn't preserve order/sequence
  2. https://leetcode.com/problems/apply-operations-to-an-array/description/
    • Check Note that the operations are applied sequentially, not all at once.

Upcoming​

  1. codeforces.com/contest/2203/problem/B
    • Intitution was right, just couldn't impelement it
    • Check the constraint(input the integer as string)
    • Sort it, reduce the large digits from sum, special consideration for first character in string
  2. codeforces.com/contest/2202/problem/A
    • Using both (+2,+1) and (+4,-1) is equivalent to using two (+3,0) moves.
  3. codeforces.com/problemset/problem/1363/A
  4. codeforces.com/problemset/problem/1092/B
  5. codeforces.com/problemset/problem/1335/A
  6. codeforces.com/problemset/problem/1335/C
  7. codeforces.com/problemset/problem/1421/A
  8. codeforces.com/problemset/problem/110/A
  9. codeforces.com/problemset/problem/122/A
  10. codeforces.com/problemset/problem/1176/A
  11. codeforces.com/problemset/problem/1095/A
  12. codeforces.com/problemset/problem/1348/A
  13. leetcode.com/problems/number-of-even-and-odd-bits/
  14. geeksforgeeks.org/problems/string-comparison5858/1
  15. two pointer: geeksforgeeks.org/problems/palindrome-string0817/1
  16. two pointer: geeksforgeeks.org/problems/string-concatenation-1614157859/1
  17. https://www.geeksforgeeks.org/problems/remove-spaces0128/1
  18. https://www.geeksforgeeks.org/problems/maximum-occuring-character-1587115620/1
  19. https://leetcode.com/problems/finding-pairs-with-a-certain-sum/description/