Sit down. Hold a cup of coffee.
Look at code and think.

Think-sip-repeat.

Three implementations, one of them right. The other two differ by two to five lines — solve it and you see what all three return on an input that tells them apart.

46 questions

Name the problem

Every card holds a classic interview problem with its names stripped out. Probe it with inputs until you know what it does, then name it from the full list of 150.

ProblemDifficulty

Problem 1EasyEasy
Problem 2EasyEasy
Problem 3EasyEasy
Problem 4EasyEasy
Problem 5EasyEasy
Problem 6EasyEasy
Problem 7HardHard
Problem 8EasyEasy
Problem 9MediumMedium
Problem 10MediumMedium
Problem 11MediumMedium
Problem 12MediumMedium
Problem 13MediumMedium
Problem 14MediumMedium
Problem 15MediumMedium
Problem 16MediumMedium
Problem 17MediumMedium
Problem 18MediumMedium
Problem 19MediumMedium
Problem 20MediumMedium
Problem 21MediumMedium
Problem 22MediumMedium
Problem 23HardHard
Problem 24MediumMedium
Problem 25HardHard
Problem 26MediumMedium
Problem 27EasyEasy
Problem 28MediumMedium
Problem 29EasyEasy
Problem 30HardHard
Problem 31MediumMedium
Problem 32MediumMedium
Problem 33MediumMedium
Problem 34MediumMedium
Problem 35MediumMedium
Problem 36MediumMedium
Problem 37MediumMedium
Problem 38MediumMedium
Problem 39MediumMedium
Problem 40HardHard
Problem 41MediumMedium
Problem 42EasyEasy
Problem 43HardHard
Problem 44MediumMedium
Problem 45HardHard
Problem 46MediumMedium
Problem 47HardHard
Problem 48MediumMedium
Problem 49MediumMedium
Problem 50MediumMedium
Problem 51MediumMedium
Problem 52MediumMedium
Problem 53MediumMedium
Problem 54EasyEasy
Problem 55EasyEasy
Problem 56MediumMedium
Problem 57EasyEasy
Problem 58MediumMedium
Problem 59MediumMedium
Problem 60MediumMedium
Problem 61EasyEasy
Problem 62MediumMedium
Problem 63MediumMedium
Problem 64MediumMedium
Problem 65MediumMedium
Problem 66MediumMedium
Problem 67MediumMedium
Problem 68MediumMedium
Problem 69EasyEasy
Problem 70MediumMedium
Problem 71MediumMedium
Problem 72MediumMedium
Problem 73HardHard
Problem 74MediumMedium
Problem 75MediumMedium
Problem 76MediumMedium
Problem 77MediumMedium
Problem 78EasyEasy
Problem 79MediumMedium
Problem 80MediumMedium
Problem 81HardHard
Problem 82MediumMedium
Problem 83HardHard
Problem 84MediumMedium
Problem 85MediumMedium
Problem 86EasyEasy
Problem 87HardHard
Problem 88EasyEasy
Problem 89MediumMedium
Problem 90MediumMedium
Problem 91MediumMedium
Problem 92MediumMedium
Problem 93MediumMedium
Problem 94EasyEasy
Problem 95HardHard
Problem 96MediumMedium
Problem 97EasyEasy
Problem 98EasyEasy
Problem 99EasyEasy
Problem 100HardHard
Problem 101MediumMedium
Problem 102MediumMedium
Problem 103MediumMedium
Problem 104MediumMedium
Problem 105MediumMedium
Problem 106EasyEasy
Problem 107MediumMedium
Problem 108MediumMedium
Problem 109MediumMedium
Problem 110MediumMedium
Problem 111EasyEasy
Problem 112MediumMedium
Problem 113MediumMedium
Problem 114HardHard
Problem 115MediumMedium
Problem 116MediumMedium
Problem 117MediumMedium
Problem 118HardHard
Problem 119MediumMedium
Problem 120MediumMedium
Problem 121EasyEasy
Problem 122MediumMedium
Problem 123MediumMedium
Problem 124EasyEasy
Problem 125MediumMedium
Problem 126HardHard
Problem 127MediumMedium
Problem 128MediumMedium
Problem 129MediumMedium
Problem 130MediumMedium
Problem 131MediumMedium
Problem 132MediumMedium
Problem 133MediumMedium
Problem 134HardHard
Problem 135MediumMedium
Problem 136EasyEasy
Problem 137EasyEasy
Problem 138MediumMedium
Problem 139MediumMedium
Problem 140MediumMedium
Problem 141HardHard
Problem 142MediumMedium
Problem 143MediumMedium
Problem 144HardHard
Problem 145MediumMedium
Problem 146MediumMedium
Problem 147MediumMedium
Problem 148MediumMedium
Problem 149HardHard
Problem 150MediumMedium

Sit down. Hold a cup of coffee.Look at code and think.

Name the problem

Sit down. Hold a cup of coffee.
Look at code and think.