Daily Coding Problem: Get exceptionally good at coding interviews by solving one problem every day

300 Pages·2019·8.395 MB·English

by  Lawrence Wu , Alex Miller

Daily Coding Problem
Alex Miller and Lawrence Wu
1
2
Copyright© 2019, Alex Miller and Lawrence Wu
All rights reserved. No part of this book may be reproduced in any form or by any
electronic or mechanical means, including information storage and retrieval systems,
without permission in writing from the publisher, except in the case of brief quota
tions embodied in critical reviews and certain other noncommercial uses permitted
by copyright law. For more information, email the authors at founders@dailycoding
problem.com.
SECOND EDITION
ISBN 978-1-7932966-3-4
( '
Printed in the United States of America
Cover Design by Irene Zou
10987654321
Alex: For Mom, Dad,Jordan, Hannah, and Zaddy
Lawrence: For Mama and Papa
3

Contents
Contents 5
I Data Structures 17
1 Arrays 19
1.1 Get product of all other elements . 20
1.2 Locate smallest window to be sorted 22
1.3 Calculate maximum subarray sum . 24
1.4 Find number of smaller elements to the right . 26
2 Strings 29
2.1 Find anagram indices 29
2.2 Generate palindrome pairs 32
2.3 Print zigzag form . . . . . 34
2.4 Determine smallest rotated string . 36
3 Linked Lists 41
3.1 Reverse linked list ............. . 42
3.2 Add two linked lists that represent numbers 44
3.3 Rearrange a linked list to alternate high-low 46
3.4 Find intersecting nodes of linked lists . 48
4 Stacks and Qyeues 51
4.1 Implement a max stack ......... . 53
4.2 Determine whether brackets are balanced 54
4.3 Compute maximum ofk-length subarrays 56
4.4 Reconstruct array using+/- signs ..... 59
5 Hash Tables 63
5. 1 Implement an LRU cache . 65
5.2 Cut brick wall ...... . 68
5
CONTENTS 6
5.3 Implement a sparse array 70
6 Trees 73
6.1 Count unival trees . 75
6.2 Reconstruct tree from pre-order and in-order traversals 79
6.3 Evaluate arithmetic tree . . . . . . 81
6.4 Get tree level with minimum sum 83
7 Binary Search Trees 85
7 .1 Find floor and ceiling . . . . . . 87
7.2 Convert sorted array to BST .. 88
7.3 Construct all BSTs with n nodes 90
8 Tries 93
8.1 Implement autocomplete system 95
8.2 Create PrefixMapSum class . . . 98
8.3 Find Maximum XOR of element pairs 102
9 Heaps 105
9 .1 Compute the running median 107
9 .2 Find most similar websites 109
9 .3 Generate regular numbers . 111
9.4 Build a Huffman tree 113
10 Graphs 119
10.1 Determine if a cycle exists . 122
10.2 Remove edges to create even trees 124
10.3 Create stepword chain .. 126
10.4 Beat Snakes and Ladders 128
10.5 Topological sort ... 130
11 Advanced Data Structures 133
11.1 Fenwick tree ..... 134
11.2 Disjoint-set data structure 137
11.3 Bloom filter . . . . . . . . 140
II Algorithms 143
12 Recursion 145
12.1 Tower of Hanoi ....... . 146
12.2 Implement regular expressions 149
12.3 Find array extremes efficiently 151
12.4 Play Nim . . . . . . . . . . . 154
CONTENTS 7
13 Dynamic Programming 157
13.1 Number of ways to climb a staircase 160
13.2 Number of ways to decode a string 162
13.3 Painting houses . . . . . . . . . . 164
14 Backtracking 167
14.1 Compute flight itinerary 169
14.2 Solve Sudoku ..... . 171
14.3 Count Android unlock combinations . 174
15 Sorting and Searching 179
15 .1 Dutch flag problem . . . . . . . 181
15 .2 Pancake sort . . . . . . . . . . . 183
15 .3 Efficiently sort a million integers 185
15 .4 Find minimum element in rotated sorted array . 186
16 Pathfinding 189
16.1 Dijkstra's algorithm 190
16.2 Bellman-Ford . 193
16.3 Floyd-Warshall 195
17 Bit Manipulation 199
17.1 Find element that appears once in list ....... . 201
17.2 Implement division without / or * operators . . . . . 202
17.3 Compute longest consecutive string of ones in binary 204
17.4 Find nth sevenish number .............. . 205
18 Randomized Algorithms 209
18.1 Pick random element from infinite stream 210
18.2 Shuffle deck of cards 212
18.3 Markov chain .. 215
19 Advanced Algorithms 219
19.1 Rabin-Karp ... 220
19.2 Hierholzer's algorithm 224
19.3 A* search ...... . 227
III Applications 235
20 Applications 237
20.1 Ghost ..... . 238
20.2 Connect 4 ... . 241
20.3 Cryptarithmetic . 247
CONTENTS 8
20.4 Cheapest itinerary . 251
20.5 Alien dictionary .. 254
20.6 Prime numbers .. 256
20.7 Crossword puzzles. 259
20. 8 UTF-8 encodings . 263
20.9 Blackjack ..... 265
IV Design 271
21 Data Structure Design 273
21.1 Dictionary with time key 274
21.2 Qyeue with fixed-length array 278
21.3 Qyack ............ . 282
22 System Design 287
22.1 Crawl Wikipedia .......... . 288
22.2 Design a hit counter . . . . . . . . . . 293
22.3 What happens when you visit a URL? 296
Glossary 299