✅ Finalized Python Problem-Solving Template (Enhanced)

🧠 0. Understand the Problem

• Problem Statement: What exactly is asked?
• Input/Output Format: Examples + edge cases
• Constraints: Time/space limits, input size
• Keywords: Sort, Search, Max/Min, Count, Path, Decision

✏️ 1. Write Pseudocode / Flow

• Step-by-step breakdown
• Conditions / Decisions
• Use diagrams if applicable (matrix, tree, array, etc.)

🧰 2. Choose Tools

• Which data structures? Why?
• Loop or Recursion?
• Sliding Window / DP / Stack / Queue?

🧪 3. Dry Run with Mini Input

• Manually run on 1–2 inputs
• Track variable changes
• Ensure logic holds

💻 4. Code

def get_input():
    # Can be hardcoded, user, or file
    return "abba"

def process(data):
    # Core logic here
    return data == data[::-1]

def show_output(result):
    print("Is palindrome?", result)

def main():
    data = get_input()
    result = process(data)
    show_output(result)

main()

✅ 5. Test & Debug

• Add print() at each logic step
• Cover edge cases

🧠 Optional Enhancements

• Add time/space complexity as docstring
• Write unit tests
• Make reusable function if needed

🔥 200 Python Practice Problems — Template-Based Solutions

📘 Topic 1: Arrays & Strings (20 Problems)

1. Reverse a String
2. Check if a String is Palindrome
3. Reverse Words in a Sentence
4. Find Duplicate Characters
5. Count Vowels and Consonants
6. Remove Duplicates from String
7. Maximum Frequency Character
8. Longest Common Prefix
9. Anagram Check
10. Replace Spaces with ‘%20’
11. Compress String (e.g., aabcc → a2b1c2)
12. Remove a Character
13. Find First Non-Repeating Character
14. Validate Palindrome with Alphanumeric Only
15. Check Rotation of String
16. Check Balanced Parentheses
17. Group Anagrams
18. Isomorphic Strings
19. Remove Adjacent Duplicates
20. Longest Substring Without Repeating Characters

📘 Topic 2: Sliding Window (20 Problems)

1. Maximum Sum Subarray of Size K
2. First Negative Number in Every Window of Size K
3. Count Occurrences of Anagrams
4. Longest Substring with K Distinct Characters
5. Longest Repeating Character Replacement
6. Permutation in String
7. Minimum Window Substring
8. Sliding Window Maximum
9. Count of Substrings Containing All 3 Characters
10. Longest Substring with At Most Two Distinct Characters
11. Substring with Concatenation of All Words
12. Number of Subarrays of Size K with Average ≥ Threshold
13. Max Consecutive Ones III
14. Count Number of Nice Subarrays
15. Minimum Operations to Reduce X to Zero
16. Longest Subarray of 1s After Deleting One Element
17. Check If a String Contains All Binary Codes of Size K
18. Find All Anagrams in a String
19. Find K-Length Substrings with No Repeated Characters
20. Shortest Subarray with Sum at Least K

📘 Topic 3: Two Pointers (20 Problems)

1. Two Sum (Sorted Array)
2. Remove Duplicates from Sorted Array
3. Move Zeroes
4. Reverse Words in a String III
5. Valid Palindrome II
6. Merge Two Sorted Arrays
7. Container With Most Water
8. Trapping Rain Water
9. 3Sum Problem
10. 3Sum Closest
11. 4Sum Problem
12. Remove Element
13. Sort Colors (Dutch National Flag)
14. Backspace String Compare
15. Minimum Size Subarray Sum
16. Max Number of K-Sum Pairs
17. Check If N and Its Double Exist
18. Shortest Unsorted Continuous Subarray
19. Palindromic Substrings
20. Interval List Intersections

📘 Topic 4: Hashing / HashMaps (20 Problems)

1. Two Sum
2. Group Anagrams
3. Longest Consecutive Sequence
4. Subarray Sum Equals K
5. Isomorphic Strings
6. Word Pattern
7. Find All Duplicates in an Array
8. Top K Frequent Elements
9. Intersection of Two Arrays
10. Valid Sudoku
11. Find Missing Number
12. Check for Duplicates
13. Count Good Meals
14. Minimum Index Sum of Two Lists
15. Equal Row and Column Pairs
16. Maximum Number of Balloons
17. Longest Harmonious Subsequence
18. Unique Number of Occurrences
19. Count Elements with x+1 Exist
20. Find Common Characters

📘 Topic 5: Stack (20 Problems)

1. Valid Parentheses
2. Min Stack
3. Evaluate Reverse Polish Notation
4. Daily Temperatures
5. Asteroid Collision
6. Backspace String Compare
7. Remove All Adjacent Duplicates In String
8. Score of Parentheses
9. Decode String
10. Next Greater Element I
11. Next Greater Element II
12. Simplify Path
13. Remove K Digits
14. Longest Valid Parentheses
15. Basic Calculator
16. Exclusive Time of Functions
17. Baseball Game
18. Largest Rectangle in Histogram
19. Minimum Add to Make Parentheses Valid
20. Design a Stack With Increment Operation

📘 Topic 6: Recursion & Backtracking (20 Problems)

1. Factorial
2. Fibonacci Number
3. Power of a Number
4. Subsets
5. Subsets II (with duplicates)
6. Permutations
7. Permutations II
8. Combination Sum
9. Combination Sum II
10. Letter Combinations of a Phone Number
11. Palindrome Partitioning
12. Word Search
13. N-Queens
14. Sudoku Solver
15. Generate Parentheses
16. Restore IP Addresses
17. Path Sum III
18. Rat in a Maze
19. Count Unique Paths
20. Word Break Problem

📘 Topic 7: Matrix / Grid Traversal (20 Problems)

1. Spiral Matrix
2. Rotate Image
3. Set Matrix Zeroes
4. Search a 2D Matrix
5. Number of Islands
6. Max Area of Island
7. Flood Fill
8. Shortest Path in Binary Matrix
9. Word Search
10. Matrix Diagonal Sum
11. Pacific Atlantic Water Flow
12. Minimum Path Sum
13. Unique Paths
14. Robot Room Cleaner
15. Path With Minimum Effort
16. Game of Life
17. Island Perimeter
18. Count Negative Numbers in Sorted Matrix
19. Kth Smallest Element in Sorted Matrix
20. Diagonal Traverse

📘 Topic 8: Greedy Algorithms (20 Problems)

1. Activity Selection Problem
2. Fractional Knapsack
3. Jump Game
4. Gas Station
5. Candy Distribution
6. Lemonade Change
7. Assign Cookies
8. Non-overlapping Intervals
9. Minimum Number of Arrows to Burst Balloons
10. Partition Labels
11. Reorganize String
12. Maximum Units on a Truck
13. Task Scheduler
14. Split Array into Consecutive Subsequences
15. Hand of Straights
16. Valid Parenthesis String
17. IPO Problem
18. Minimum Add to Make Parentheses Valid
19. Increasing Triplet Subsequence
20. Wiggle Subsequence

📘 Topic 9: Dynamic Programming (20 Problems)

1. Fibonacci Number (Memoization & Tabulation)
2. Climbing Stairs
3. House Robber
4. House Robber II
5. Longest Palindromic Substring
6. Longest Common Subsequence
7. Longest Increasing Subsequence
8. Coin Change
9. Coin Change II
10. Partition Equal Subset Sum
11. Decode Ways
12. Edit Distance
13. Palindromic Substrings
14. Best Time to Buy and Sell Stock
15. Maximum Subarray
16. Jump Game
17. Unique Paths
18. Interleaving String
19. Minimum Path Sum
20. Target Sum

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