I love code snippet challenges
I stumbled upon a blog with a random code snippet challenge. Here was the problem at hand:
Given a String (x) containing only characters a-z, write a function (f) that returns a base 10 integer, which converts the String as if it were a base 26 numeral. Function f is bijective.
I wanted to give it a stab in javascript not because it sounded particularly difficult but to play with different javascript code styles. Here’s my 4 versions:
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function f(i) {
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if (!i) { return 0; }
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var parts, n, pow, val;
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parts = i.split(”);
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parts.reverse();
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val = 0;
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pow = 1;
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for (n = 0; n < parts.length; ++n) {
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val += pow * (parts[n].charCodeAt(0) - 96);
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pow = pow * 26;
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}
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return val;
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}
The first one turns the string into an array and reverses it before doing the math loop. My next try eliminates the array and iterates backwards over the string.
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function f(i) {
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if (!i) { return 0; }
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var n, mult = 1, val = 0, offset = 96, base = 26;
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for (n = i.length - 1; n > -1; n–) {
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val += mult * (i.charCodeAt(n) - offset);
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mult = mult * base;
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}
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return val;
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}
Here I’m playing with chaining array functions. While I don’t create an array, this is very similar to the first try.
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function f(i) {
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if (!i) { return 0; }
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var mult = 1, val = 0, offset = 96, base = 26;
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i.split(”).reverse().forEach(function(el) {
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val += mult * (el.charCodeAt(0) - offset);
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mult = mult * base;
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});
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return val;
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}
Finally, recursion instead of an iterative loop.
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function f(i, mult) {
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if (!i) { return 0; }
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if (!mult) { mult = 1; }
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var offset = 96, base = 26;
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return mult * (i.charCodeAt(i.length - 1) - offset)
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+ f(i.substr(0, i.length - 1), mult * base);
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}
Checkout the test output of my functions. Works in Firefox 1.5+ or other browsers that implement more modern javascript functions. Shouldn’t work in IE.