Diving In

Just as regular expressions put strings on steroids, the itertools module puts iterators on steroids. But first, I want to show you a classic puzzle.

HAWAII + IDAHO + IOWA + OHIO == STATES
510199 + 98153 + 9301 + 3593 == 621246

H = 5
A = 1
W = 0
I = 9
D = 8
O = 3
S = 6
T = 2
E = 4

Puzzles like this are called cryptarithms or alphametics. The letters spell out actual words, but if you replace each letter with a digit from 0–9, it also “spells” an arithmetic equation. The trick is to figure out which letter maps to each digit. All the occurrences of each letter must map to the same digit, no digit can be repeated, and no “word” can start with the digit 0.

The most well-known alphametic puzzle is SEND + MORE = MONEY.

In this chapter, we’ll dive into an incredible Python program originally written by Raymond Hettinger. This program solves alphametic puzzles in just 14 lines of code.