🧠 D-Day 09 – Leetcode Dynamic Programming & Graph Series (Python) 📘 Overview

This repository contains Day 09 solutions from my 100-Day Leetcode Mastery Plan (Python Only). Each problem includes:

Clear problem explanation

Optimized Python solution

Detailed step-by-step comments

Time and Space Complexity analysis

All problems focus on Dynamic Programming, Graphs, and Greedy topics — essential for mastering FAANG-level interviews and competitive programming.

🧩 Problem Set (Solved)

#	Problem	File	Topics
1	Decode Ways	_01_decode_ways_91.py	DP, String
2	Word Break	_02_word_break_139.py	DP, HashSet
3	Maximum Product Subarray	_03_maximum_product_subarray_152.py	DP, Kadane’s Algorithm
4	House Robber	_04_house_robber_198.py	DP, Array
5	Maximal Square	_05_maximal_square_221.py	DP, Matrix
6	Perfect Squares	_06_perfect_square_276.py	DP, Math
7	Best Time to Buy and Sell with Cooldown	_07_best_time_to_buy_and_sell_when_cooldown_309.py	DP, State Machine
8	Coin Change II	_08_coin_change_ll_518.py	DP, Combinations
9	Palindromic Substring	_09_palindromic_substring_647.py	DP, String
10	Maximum Length of Repeated Subarray	_10_maximum_length_of_repeated_subarray_719.py	DP, Arrays
11	Division Game	_11_division_game_1025.py	Game Theory, DP
12	N-th Tribonacci Number	_12_N-th_Tribonacci_Number_1137.py	DP, Recursion
13	Minimum Falling Path Sum	_13_minimum_falling_path_sum_931.py	DP, Matrix
14	Unique Paths	_14_unique_paths_62.py	DP, Combinatorics
15	Unique Paths II	_15_unique_paths_ll_63.py	DP, Grid
16	Interleaving String	_16_interleaving_string_97.py	DP, String

⚙️ Environment Setup

To run any solution: python _01_decode_ways_91.py

Make sure you have Python 3.9+ installed.

📈 Learning Focus

Dynamic Programming (Bottom-Up, Top-Down)

Space Optimization Techniques

Tabulation & Memoization

Graph Traversal via DP (where applicable)

Leetcode-style clean and optimal code writing

💡 Author

👨‍💻 Shankar Kumar AI & ML | Data Structures | Leetcode | Competitive Programming 🔗 GitHub | LinkedIn | X (Twitter)