Use este recorte para treinar problemas de live coding que cobram raciocínio em voz alta, clareza de solução, complexidade e casos de borda.
Treine problemas clássicos com foco em clareza, complexidade e comunicação ao vivo.
Explique a abordagem antes de tocar no código.
Compare a solução inicial com a otimização que você quer perseguir.
Teste casos de borda em voz alta e ajuste rápido quando perceber um bug.
Este recorte reúne perguntas reais desse tema para você treinar com contexto mais específico e ver padrões que costumam se repetir.
Given two non-negative integers as decimal strings, return their sum as a string by simulating digit-by-digit addition from the least significant digits with carry (no integer conversion or big-integer libraries allowed). Inputs can be large (length up to 10^4), so the solution must handle arbitrary-length strings.
Estruture solução, trade-offs e complexidade com clareza.
Return the power set of a unique-element integer array by enumerating all 2^n subsets (typical solutions use backtracking/DFS or bitmask iteration), noting the exponential output is acceptable since n ≤ 10.
Estruture solução, trade-offs e complexidade com clareza.
Check whether the characters in pattern and the space-separated words in s have a bijective (one-to-one and onto) mapping that preserves order — i.e., each pattern letter maps to exactly one word and no two letters map to the same word, and substituting letters with their mapped words reproduces s.
Estruture solução, trade-offs e complexidade com clareza.
Reorder an array of values 0, 1, and 2 in-place so all 0s come first, then 1s, then 2s (the Dutch National Flag problem); aim for a one-pass, constant-extra-space solution without using built-in sort.
Estruture solução, trade-offs e complexidade com clareza.
Given signed integers for asteroid sizes and directions, determine which asteroids remain after sequential collisions where only opposite-moving neighbors (positive then negative) meet and the smaller (or both if equal) explode; this is typically solved by simulating collisions with a stack.
Estruture solução, trade-offs e complexidade com clareza.
Rearrange the array in-place so all zeros are moved to the end while preserving the relative order of non-zero elements, without using extra storage. Aim to minimize the number of writes/operations (stable partition / two-pointer pattern).
Estruture solução, trade-offs e complexidade com clareza.
Determine whether a binary tree contains a root-to-leaf path whose node values add up to a given targetSum. (A leaf is a node with no children.)
Estruture solução, trade-offs e complexidade com clareza.
Find all unique triplets in an integer array that sum to zero, ensuring no duplicate triplets in the output. The core challenge is efficiently enumerating combinations (commonly done by sorting and using a two-pointer scan) within the 3 ≤ n ≤ 3000 constraint.
Estruture solução, trade-offs e complexidade com clareza.
Simulate a Minesweeper click on an m×n board: clicking a mine turns it to 'X', while clicking an empty square requires counting adjacent mines — if the count > 0 set the cell to that digit, otherwise mark it 'B' and recursively reveal all neighbors. The core challenge is a grid flood-fill with adjacency counting (use DFS/BFS) to propagate reveals.
Estruture solução, trade-offs e complexidade com clareza.
Given sorted stone positions and an initial jump of 1, determine whether a frog can reach the last stone when each jump length must be k-1, k, or k+1 from the previous jump. The core challenge is exploring reachable jump sizes per stone under position gaps — typically solved with dynamic programming/DFS using a map/set of stones to reachable jump lengths.
Given an array where each value is the maximum jump length from that index, determine whether you can reach the last index starting from the first; the core challenge is tracking the furthest reachable index (greedy/range propagation) to avoid exploring all paths.
Return all strings in the list that can be formed by concatenating at least two other words from the same list. This is a word-break style problem (use DP/trie + memoization) to efficiently test each word given total input size up to 1e5.
Given a digit string, count how many ways it can be segmented into valid codes 1–26 (two-digit codes cannot start with '0'), handling invalid zeros and impossible encodings — a classic dynamic-programming/counting-over-partitions problem.
Given a rectangular grid with exactly one island of orthogonally connected land cells, compute the island's perimeter by summing the edges of land cells that are adjacent to water or the grid boundary (equivalently use 4*land_cells - 2*shared_edges). Grid dimensions ≤100 and connections are only horizontal/vertical.
Place k mailboxes on a line to minimize the sum of distances from each house to its nearest mailbox; optimal placement partitions the sorted houses into k contiguous groups served by a mailbox at each group's median, solvable by dynamic programming with precomputed interval costs.
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