Lis

2 articles

dsa7 min read

Russian Doll Envelopes — 2D LIS with the Tie-Breaker Trick

LeetCode 354 Russian Doll Envelopes is a sneaky 2D Longest Increasing Subsequence problem. Sort by width ascending and height descending so equal widths cannot stack, then run patience-sort LIS on heights for an O(n log n) DP solution beloved by FAANG interviewers.

March 19, 2026Read →

dsa9 min read

Number of Longest Increasing Subsequences — DP, Segment Tree & BIT Solutions

Count all longest increasing subsequences with DP in O(n^2) or with a segment tree on values for O(n log n). The classic crossover problem between DP and range-query data structures.

March 19, 2026Read →