| 2-1fibonacci | Fibonacci sequence | 509. Fibonacci Number | Compute the n-th Fibonacci number efficiently. |
| 2-3gcd | Greatest Common Divisor | 1979. Find Greatest Common Divisor of Array | Find the GCD of numbers using the Euclidean algorithm. |
| 2-4lcm | Least Common Multiple | 2413. Smallest Even Multiple — simplified LCM case | Compute LCM (e.g., of n and 2) via a*b//gcd(a,b). |
| 2-4lcm (advanced variant) | Replace adjacent non-coprime numbers with their LCM | 2197. Replace Non-Coprime Numbers in Array | Uses LCM repeatedly to merge numbers into coprime sequence. |
| 3-1change | Minimum coins to make change | 322. Coin Change | Compute the minimum number of coins needed to make a target sum. |
| 3-2fractional_knapsack | Fractional knapsack (greedy) | 1710. Maximum Units on a Truck | Sort by value density and take as much as fits — same greedy pattern. |
| 3-4covering_segments | Minimum points to cover intervals | 452. Minimum Number of Arrows to Burst Balloons | Select minimum points to cover all segments (interval greedy). |
| 3-6largest_number | Arrange numbers to form the largest integer | 179. Largest Number | Sort strings by custom comparator to form the maximum concatenated number. |
| 4-1binary_search | Binary search | 704. Binary Search | Classic binary search in a sorted array. |
| 4-2majority_element | Majority element (> n/2 occurrences) | 169. Majority Element | Find element appearing more than ⌊n/2⌋ times using Boyer–Moore algorithm. |
| 4-4inversions | Count inversions using merge sort | 493. Reverse Pairs | Similar divide-and-conquer pattern for counting pair inversions. |
| 4-5points_and_segments | Count how many segments cover each point | 436. Find Right Interval or 850. Rectangle Area II (conceptually related to interval sweep-line problems) | Uses sweep line / sorting technique to track interval coverage. |
| 4-6closest | Closest pair of points in plane | 973. K Closest Points to Origin (conceptually related) | Find minimal Euclidean distance between two points (divide and conquer). |
| 5-1change_dp | Minimum coins to make change (DP) | 322. Coin Change | Classic DP problem: compute minimum coins to reach target amount. |
| 5-3edit_distance | Edit (Levenshtein) distance | 72. Edit Distance | Compute min operations (insert, delete, replace) to convert string A → B. |
| 5-4lcs2 | Longest Common Subsequence (2 strings) | 1143. Longest Common Subsequence | Standard DP to find LCS length between two strings. |
| 6-1knapsack | 0/1 Knapsack problem | 416. Partition Equal Subset Sum or 494. Target Sum | Both are DP problems built on the 0/1 knapsack principle (subset-sum DP). |
| 6-2partition3 | Partition array into 3 equal-sum subsets | 698. Partition to K Equal Sum Subsets | Generalized k-partition problem using backtracking/DP. |
| 6-3placing_parentheses | Maximize expression value by optimal parentheses placement | 241. Different Ways to Add Parentheses | DP over operator partitions to find max/min expression value. |