Kaushik's Notes

DSA 90-Day

4 min read

Phase 1 — Graph Mastery (Day 1–20)

Target: Complete CSES Graph Algorithms + Key LeetCode Graph Hards

Day 1 — BFS & Multi-Source BFS

CSES:

  1. Labyrinth
  2. Message Route

LeetCode:

Day 2 — Dijkstra Basics

CSES:

  1. Shortest Routes I
  2. Flight Discount

LeetCode:

Day 3 — Bellman-Ford & Negative Cycles

CSES:

  1. Shortest Routes II (Floyd-Warshall)
  2. Cycle Finding

LeetCode:

Day 4 — Topological Sorting

CSES:

  1. Course Schedule (Khans ALgorith) - In_degree
  2. Longest Flight Route

LeetCode:

Day 5 — Strongly Connected Components

CSES:

  1. Planets and Kingdoms (Kosaraju)
  2. [] Giant Pizza Solution Link - 2-SAT Problem

LeetCode:

Day 6 — Bridges & Articulation Points

CSES:

  1. Flight Routes Check
  2. Road Construction (DSU)

LeetCode:

Day 7 — Minimum Spanning Tree

CSES:

  1. Road Reparation
  2. [Road Construction](repeat for MST version)

LeetCode:

Day 8 — Advanced BFS/0-1 BFS

CSES:

  1. High Score
  2. Game Routes

LeetCode:

Day 9 — DSU Rollback / Offline

CSES:

  1. Dynamic Connectivity
  2. School Dance

LeetCode:

Day 10 — Graph Recap Contest

  • Pick 4 unsolved/mistakes from last 9 days
  • Solve in 2.5 hrs timed
  • Review all Graph notes

Day 11 — Multi-Source + State BFS

CSES:

  1. Monsters
  2. Police Chase

LeetCode:

Day 12 — Flow Basics

CSES:

  1. Download Speed (Max Flow)
  2. Police Chase II

LeetCode:

Day 13 — Flow & Matching

CSES:

  1. School Dance (Matching)

  2. Distinct Routes

LeetCode:

Day 14 — Advanced Graph Mix

CSES:

  1. Game Routes
  2. Flight Routes

LeetCode:

Day 15 — Graph Contest

Task:

  • 4 problems: 2 CSES + 2 LeetCode Hard in 3 hrs.

  • Full post-mortem.

Day 16–20:

 Graph Revision + Weak Point Drills

  • Day 16: CSES repeat MST + DSU

  • Day 17: CSES repeat SCC + Bridges

  • Day 18: LeetCode Hard BFS/DFS mix

  • Day 19: LeetCode Hard Dijkstra/DP hybrid

  • Day 20: Full Graph Mock Contest

Phase 2 – Advanced DP (Day 21–40)

Day 21 — Bitmask DP Basics

CSES:

  1. Hamiltonian Flights
  2. Counting Tilings

LeetCode:

Day 22 — DP on Trees

CSES:

  1. Tree Matching
  2. Tree Diameter

LeetCode:

Day 23 — Digit DP

CSES:

  1. Counting Numbers
  2. Counting Sequences

LeetCode:

Day 24–28 — DP Mixed Sets

  • Knuth Optimization
  • Probability DP
  • State Compression

Example: LeetCode: 312 (Burst Balloons), 1547 (Min Cost to Cut Stick), 1220 (Count Vowel Permutations), 188 (Stock IV), 2218 (Max Value of K Coins)

Day 29–30 — DP Mock

  • Day 29: 4 advanced DP problems
  • Day 30: Mixed DP + Graph in 3 hr mock

Phase 3 – Mixed Advanced (Day 41–65)

Day 41–45 — Segment Tree / BIT

CSES:

  1. Dynamic Range Sum Queries
  2. Dynamic Range Minimum Queries
  3. Polynomial Queries

LeetCode:

  • 307, 315, 493, 327 (all segment tree/BIT)

Day 46–50 — Mo’s Algorithm & Offline Queries

  • CSES Range Queries advanced problems
  • LeetCode hard prefix/suffix trick problems

Day 51–55 — Backtracking + Pruning

  • CSES combinatorics problems
  • LeetCode: N-Queens II, Word Search II, Remove Invalid Parentheses, Sudoku Solver

Day 56–60 — Greedy + Proof Problems

  • CSES Greedy advanced
  • LeetCode Hard Greedy: 135, 164, 630, 757

Day 61–65 — Mixed Practice

  • Each day: 1 Graph, 1 DP, 1 Data Structure
  • Time cap: 35–40 min/problem

Phase 4 – Hardcore Interview Simulations (Day 66–90)

Daily Flow:

  • Problem 1 (Hard Graph) — 40 min
  • Problem 2 (Hard DP) — 40 min
  • Problem 3 (Mixed Advanced) — 40 min
  • Problem 4 (Medium speed) — 25 min

Weekly:

  • 2x Mock Interviews on Pramp/Interviewing.io
  • Friday night: Review all mistakes + pattern doc
  • Sunday morning: Full 3 hr contest

Final Week (Day 85–90):

  • Day 85–87 → Company-specific sets (Google, Meta)
  • Day 88–89 → 6 hr mock interview day
  • Day 90 → Chill + light revision of notes

Graph View

Backlinks