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Practice › LeetCode › LeetCode (archived) › LeetCode 05xx ›

LeetCode 519: Random Flip Matrix

Problem Restatement We are given a binary matrix with: m rows n columns Initially, every cell contains: 0 We need to design a data structure supporting two operations. Operations flip() Randomly choose one remaining cell containing 0 . Change it to: 1 Return its coordinates. Every remaining zero cell must have equal probability of being chosen. reset() Set all cells back to: 0 The official problem asks us to randomly...

Programming › Algorithm Cookbook › Chapter 5. Hashing and Maps ›

5.18 Attack Resistance

5.18 Attack Resistance Problem Hash tables usually provide expected constant time operations. That expectation depends on the assumption that keys are well distributed across buckets. When inputs are controlled by an adversary, this assumption may fail. You need a hash table strategy that remains safe when attackers can choose keys deliberately. Solution Use a keyed hash function or a collision-resistant table strategy for untrusted inputs. A keyed hash includes a...