7.11 — Interview Questions: Hashing

<< Overview

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Beginner

Q1. Set time O?

Answer: O(1) avg for add/has/delete

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Beginner

Q2. Map vs Object?

Answer: Map: any key type, ordered, .size

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Beginner

Q3. Two Sum with Map?

Answer: Store complement, check on iteration

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Beginner

Q4. Set for duplicates?

Answer: Add to set, check if already present

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Beginner

Q5. Hash collision?

Answer: Chaining or open addressing

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Intermediate

Q6. Longest consecutive?

Answer: Set + only start sequences (no n-1)

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Intermediate

Q7. Group anagrams?

Answer: Sorted string as map key

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Intermediate

Q8. Subarray sum K?

Answer: Prefix sum map

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Intermediate

Q9. Map iteration?

Answer: for (const [k,v] of map)

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Intermediate

Q10. When hash degrades?

Answer: Many collisions → O(n) worst case

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Quick-fire table

#	Question	Answer
1	Set time O?	O(1) avg for add/has/delete
2	Map vs Object?	Map: any key type, ordered, .size
3	Two Sum with Map?	Store complement, check on iteration
4	Set for duplicates?	Add to set, check if already present
5	Hash collision?	Chaining or open addressing
6	Longest consecutive?	Set + only start sequences (no n-1)
7	Group anagrams?	Sorted string as map key
8	Subarray sum K?	Prefix sum map
9	Map iteration?	for (const [k,v] of map)
10	When hash degrades?	Many collisions → O(n) worst case

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Rapid self-check cards

SC-001

• Q: Set time O?
• A: O(1) avg for add/has/delete

SC-002

• Q: Map vs Object?
• A: Map: any key type, ordered, .size

SC-003

• Q: Two Sum with Map?
• A: Store complement, check on iteration

SC-004

• Q: Set for duplicates?
• A: Add to set, check if already present

SC-005

• Q: Hash collision?
• A: Chaining or open addressing

SC-006

• Q: Longest consecutive?
• A: Set + only start sequences (no n-1)

SC-007

• Q: Group anagrams?
• A: Sorted string as map key

SC-008

• Q: Subarray sum K?
• A: Prefix sum map

SC-009

• Q: Map iteration?
• A: for (const [k,v] of map)

SC-010

• Q: When hash degrades?
• A: Many collisions → O(n) worst case

SC-011

• Q: Set time O?
• A: O(1) avg for add/has/delete

SC-012

• Q: Map vs Object?
• A: Map: any key type, ordered, .size

SC-013

• Q: Two Sum with Map?
• A: Store complement, check on iteration

SC-014

• Q: Set for duplicates?
• A: Add to set, check if already present

SC-015

• Q: Hash collision?
• A: Chaining or open addressing

SC-016

• Q: Longest consecutive?
• A: Set + only start sequences (no n-1)

SC-017

• Q: Group anagrams?
• A: Sorted string as map key

SC-018

• Q: Subarray sum K?
• A: Prefix sum map

SC-019

• Q: Map iteration?
• A: for (const [k,v] of map)

SC-020

• Q: When hash degrades?
• A: Many collisions → O(n) worst case

SC-021

• Q: Set time O?
• A: O(1) avg for add/has/delete

SC-022

• Q: Map vs Object?
• A: Map: any key type, ordered, .size

SC-023

• Q: Two Sum with Map?
• A: Store complement, check on iteration

SC-024

• Q: Set for duplicates?
• A: Add to set, check if already present

SC-025

• Q: Hash collision?
• A: Chaining or open addressing

SC-026

• Q: Longest consecutive?
• A: Set + only start sequences (no n-1)

SC-027

• Q: Group anagrams?
• A: Sorted string as map key

SC-028

• Q: Subarray sum K?
• A: Prefix sum map

SC-029

• Q: Map iteration?
• A: for (const [k,v] of map)

SC-030

• Q: When hash degrades?
• A: Many collisions → O(n) worst case

SC-031

• Q: Set time O?
• A: O(1) avg for add/has/delete

SC-032

• Q: Map vs Object?
• A: Map: any key type, ordered, .size

SC-033

• Q: Two Sum with Map?
• A: Store complement, check on iteration

SC-034

• Q: Set for duplicates?
• A: Add to set, check if already present

SC-035

• Q: Hash collision?
• A: Chaining or open addressing

SC-036

• Q: Longest consecutive?
• A: Set + only start sequences (no n-1)

SC-037

• Q: Group anagrams?
• A: Sorted string as map key

SC-038

• Q: Subarray sum K?
• A: Prefix sum map

SC-039

• Q: Map iteration?
• A: for (const [k,v] of map)

SC-040

• Q: When hash degrades?
• A: Many collisions → O(n) worst case

SC-041

• Q: Set time O?
• A: O(1) avg for add/has/delete

SC-042

• Q: Map vs Object?
• A: Map: any key type, ordered, .size

SC-043

• Q: Two Sum with Map?
• A: Store complement, check on iteration

SC-044

• Q: Set for duplicates?
• A: Add to set, check if already present

SC-045

• Q: Hash collision?
• A: Chaining or open addressing

SC-046

• Q: Longest consecutive?
• A: Set + only start sequences (no n-1)

SC-047

• Q: Group anagrams?
• A: Sorted string as map key

SC-048

• Q: Subarray sum K?
• A: Prefix sum map

SC-049

• Q: Map iteration?
• A: for (const [k,v] of map)

SC-050

• Q: When hash degrades?
• A: Many collisions → O(n) worst case

SC-051

• Q: Set time O?
• A: O(1) avg for add/has/delete

SC-052

• Q: Map vs Object?
• A: Map: any key type, ordered, .size

SC-053

• Q: Two Sum with Map?
• A: Store complement, check on iteration

SC-054

• Q: Set for duplicates?
• A: Add to set, check if already present

SC-055

• Q: Hash collision?
• A: Chaining or open addressing

SC-056

• Q: Longest consecutive?
• A: Set + only start sequences (no n-1)

SC-057

• Q: Group anagrams?
• A: Sorted string as map key

SC-058

• Q: Subarray sum K?
• A: Prefix sum map

SC-059

• Q: Map iteration?
• A: for (const [k,v] of map)

SC-060

• Q: When hash degrades?
• A: Many collisions → O(n) worst case

SC-061

• Q: Set time O?
• A: O(1) avg for add/has/delete

SC-062

• Q: Map vs Object?
• A: Map: any key type, ordered, .size

SC-063

• Q: Two Sum with Map?
• A: Store complement, check on iteration

SC-064

• Q: Set for duplicates?
• A: Add to set, check if already present

SC-065

• Q: Hash collision?
• A: Chaining or open addressing

SC-066

• Q: Longest consecutive?
• A: Set + only start sequences (no n-1)

SC-067

• Q: Group anagrams?
• A: Sorted string as map key

SC-068

• Q: Subarray sum K?
• A: Prefix sum map

SC-069

• Q: Map iteration?
• A: for (const [k,v] of map)

SC-070

• Q: When hash degrades?
• A: Many collisions → O(n) worst case

SC-071

• Q: Set time O?
• A: O(1) avg for add/has/delete

SC-072

• Q: Map vs Object?
• A: Map: any key type, ordered, .size

SC-073

• Q: Two Sum with Map?
• A: Store complement, check on iteration

SC-074

• Q: Set for duplicates?
• A: Add to set, check if already present

SC-075

• Q: Hash collision?
• A: Chaining or open addressing

SC-076

• Q: Longest consecutive?
• A: Set + only start sequences (no n-1)

SC-077

• Q: Group anagrams?
• A: Sorted string as map key

SC-078

• Q: Subarray sum K?
• A: Prefix sum map

SC-079

• Q: Map iteration?
• A: for (const [k,v] of map)

SC-080

• Q: When hash degrades?
• A: Many collisions → O(n) worst case

SC-081

• Q: Set time O?
• A: O(1) avg for add/has/delete

SC-082

• Q: Map vs Object?
• A: Map: any key type, ordered, .size

SC-083

• Q: Two Sum with Map?
• A: Store complement, check on iteration

SC-084

• Q: Set for duplicates?
• A: Add to set, check if already present

SC-085

• Q: Hash collision?
• A: Chaining or open addressing

SC-086

• Q: Longest consecutive?
• A: Set + only start sequences (no n-1)

SC-087

• Q: Group anagrams?
• A: Sorted string as map key

SC-088

• Q: Subarray sum K?
• A: Prefix sum map

SC-089

• Q: Map iteration?
• A: for (const [k,v] of map)

SC-090

• Q: When hash degrades?
• A: Many collisions → O(n) worst case

SC-091

• Q: Set time O?
• A: O(1) avg for add/has/delete

SC-092

• Q: Map vs Object?
• A: Map: any key type, ordered, .size

SC-093

• Q: Two Sum with Map?
• A: Store complement, check on iteration

SC-094

• Q: Set for duplicates?
• A: Add to set, check if already present

SC-095

• Q: Hash collision?
• A: Chaining or open addressing

SC-096

• Q: Longest consecutive?
• A: Set + only start sequences (no n-1)

SC-097

• Q: Group anagrams?
• A: Sorted string as map key

SC-098

• Q: Subarray sum K?
• A: Prefix sum map

SC-099

• Q: Map iteration?
• A: for (const [k,v] of map)

SC-100

• Q: When hash degrades?
• A: Many collisions → O(n) worst case

SC-101

• Q: Set time O?
• A: O(1) avg for add/has/delete

SC-102

• Q: Map vs Object?
• A: Map: any key type, ordered, .size

SC-103

• Q: Two Sum with Map?
• A: Store complement, check on iteration

SC-104

• Q: Set for duplicates?
• A: Add to set, check if already present

SC-105

• Q: Hash collision?
• A: Chaining or open addressing

SC-106

• Q: Longest consecutive?
• A: Set + only start sequences (no n-1)

SC-107

• Q: Group anagrams?
• A: Sorted string as map key

SC-108

• Q: Subarray sum K?
• A: Prefix sum map

SC-109

• Q: Map iteration?
• A: for (const [k,v] of map)

SC-110

• Q: When hash degrades?
• A: Many collisions → O(n) worst case

SC-111

• Q: Set time O?
• A: O(1) avg for add/has/delete

SC-112

• Q: Map vs Object?
• A: Map: any key type, ordered, .size

SC-113

• Q: Two Sum with Map?
• A: Store complement, check on iteration

SC-114

• Q: Set for duplicates?
• A: Add to set, check if already present

SC-115

• Q: Hash collision?
• A: Chaining or open addressing

SC-116

• Q: Longest consecutive?
• A: Set + only start sequences (no n-1)

SC-117

• Q: Group anagrams?
• A: Sorted string as map key

SC-118

• Q: Subarray sum K?
• A: Prefix sum map

SC-119

• Q: Map iteration?
• A: for (const [k,v] of map)

SC-120

• Q: When hash degrades?
• A: Many collisions → O(n) worst case

SC-121

• Q: Set time O?
• A: O(1) avg for add/has/delete

SC-122

• Q: Map vs Object?
• A: Map: any key type, ordered, .size

SC-123

• Q: Two Sum with Map?
• A: Store complement, check on iteration

SC-124

• Q: Set for duplicates?
• A: Add to set, check if already present

SC-125

• Q: Hash collision?
• A: Chaining or open addressing

SC-126

• Q: Longest consecutive?
• A: Set + only start sequences (no n-1)

SC-127

• Q: Group anagrams?
• A: Sorted string as map key

SC-128

• Q: Subarray sum K?
• A: Prefix sum map

SC-129

• Q: Map iteration?
• A: for (const [k,v] of map)

SC-130

• Q: When hash degrades?
• A: Many collisions → O(n) worst case

SC-131

• Q: Set time O?
• A: O(1) avg for add/has/delete

SC-132

• Q: Map vs Object?
• A: Map: any key type, ordered, .size

SC-133

• Q: Two Sum with Map?
• A: Store complement, check on iteration

SC-134

• Q: Set for duplicates?
• A: Add to set, check if already present

SC-135

• Q: Hash collision?
• A: Chaining or open addressing

SC-136

• Q: Longest consecutive?
• A: Set + only start sequences (no n-1)

SC-137

• Q: Group anagrams?
• A: Sorted string as map key

SC-138

• Q: Subarray sum K?
• A: Prefix sum map

SC-139

• Q: Map iteration?
• A: for (const [k,v] of map)

SC-140

• Q: When hash degrades?
• A: Many collisions → O(n) worst case

SC-141

• Q: Set time O?
• A: O(1) avg for add/has/delete

SC-142

• Q: Map vs Object?
• A: Map: any key type, ordered, .size

SC-143

• Q: Two Sum with Map?
• A: Store complement, check on iteration

SC-144

• Q: Set for duplicates?
• A: Add to set, check if already present

SC-145

• Q: Hash collision?
• A: Chaining or open addressing

SC-146

• Q: Longest consecutive?
• A: Set + only start sequences (no n-1)

SC-147

• Q: Group anagrams?
• A: Sorted string as map key

SC-148

• Q: Subarray sum K?
• A: Prefix sum map

SC-149

• Q: Map iteration?
• A: for (const [k,v] of map)

SC-150

• Q: When hash degrades?
• A: Many collisions → O(n) worst case

SC-151

• Q: Set time O?
• A: O(1) avg for add/has/delete

SC-152

• Q: Map vs Object?
• A: Map: any key type, ordered, .size

SC-153

• Q: Two Sum with Map?
• A: Store complement, check on iteration

SC-154

• Q: Set for duplicates?
• A: Add to set, check if already present

SC-155

• Q: Hash collision?
• A: Chaining or open addressing

SC-156

• Q: Longest consecutive?
• A: Set + only start sequences (no n-1)

SC-157

• Q: Group anagrams?
• A: Sorted string as map key

SC-158

• Q: Subarray sum K?
• A: Prefix sum map

SC-159

• Q: Map iteration?
• A: for (const [k,v] of map)

SC-160

• Q: When hash degrades?
• A: Many collisions → O(n) worst case

SC-161

• Q: Set time O?
• A: O(1) avg for add/has/delete

SC-162

• Q: Map vs Object?
• A: Map: any key type, ordered, .size

SC-163

• Q: Two Sum with Map?
• A: Store complement, check on iteration

SC-164

• Q: Set for duplicates?
• A: Add to set, check if already present

SC-165

• Q: Hash collision?
• A: Chaining or open addressing

SC-166

• Q: Longest consecutive?
• A: Set + only start sequences (no n-1)

SC-167

• Q: Group anagrams?
• A: Sorted string as map key

SC-168

• Q: Subarray sum K?
• A: Prefix sum map

SC-169

• Q: Map iteration?
• A: for (const [k,v] of map)

SC-170

• Q: When hash degrades?
• A: Many collisions → O(n) worst case

SC-171

• Q: Set time O?
• A: O(1) avg for add/has/delete

SC-172

• Q: Map vs Object?
• A: Map: any key type, ordered, .size

SC-173

• Q: Two Sum with Map?
• A: Store complement, check on iteration

SC-174

• Q: Set for duplicates?
• A: Add to set, check if already present

SC-175

• Q: Hash collision?
• A: Chaining or open addressing

SC-176

• Q: Longest consecutive?
• A: Set + only start sequences (no n-1)

SC-177

• Q: Group anagrams?
• A: Sorted string as map key

SC-178

• Q: Subarray sum K?
• A: Prefix sum map

SC-179

• Q: Map iteration?
• A: for (const [k,v] of map)

SC-180

• Q: When hash degrades?
• A: Many collisions → O(n) worst case

SC-181

• Q: Set time O?
• A: O(1) avg for add/has/delete

SC-182

• Q: Map vs Object?
• A: Map: any key type, ordered, .size

SC-183

• Q: Two Sum with Map?
• A: Store complement, check on iteration

SC-184

• Q: Set for duplicates?
• A: Add to set, check if already present

SC-185

• Q: Hash collision?
• A: Chaining or open addressing

SC-186

• Q: Longest consecutive?
• A: Set + only start sequences (no n-1)

SC-187

• Q: Group anagrams?
• A: Sorted string as map key

SC-188

• Q: Subarray sum K?
• A: Prefix sum map

SC-189

• Q: Map iteration?
• A: for (const [k,v] of map)

SC-190

• Q: When hash degrades?
• A: Many collisions → O(n) worst case

SC-191

• Q: Set time O?
• A: O(1) avg for add/has/delete

SC-192

• Q: Map vs Object?
• A: Map: any key type, ordered, .size

SC-193

• Q: Two Sum with Map?
• A: Store complement, check on iteration

SC-194

• Q: Set for duplicates?
• A: Add to set, check if already present

SC-195

• Q: Hash collision?
• A: Chaining or open addressing

SC-196

• Q: Longest consecutive?
• A: Set + only start sequences (no n-1)

SC-197

• Q: Group anagrams?
• A: Sorted string as map key

SC-198

• Q: Subarray sum K?
• A: Prefix sum map

SC-199

• Q: Map iteration?
• A: for (const [k,v] of map)

SC-200

• Q: When hash degrades?
• A: Many collisions → O(n) worst case