Created
September 14, 2019 05:31
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Encode and decode numbers into codes
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const [ns, s] = process.hrtime(); | |
const nsTime = (s * 1e6 + ns); | |
function encode(num, digits = 15, off = 0) { | |
const rand = off ? Math.random().toString(26).substring(1, 1 + off) : ''; | |
const str = (num.toString(26) + rand).split(''); | |
let input = str.map(ch => ch === '.' ? '-' : (parseInt(ch, 26) + 10).toString(36)).join('').toUpperCase(); | |
input = input.split('') | |
input.unshift('{'); | |
input.push('}'); | |
const table = []; | |
for (let x = 0; x < input.length; x++) { | |
table.push(input.slice()) | |
input.push(input.shift()); | |
} | |
table.sort(); | |
const encoded = table.map(row => row[row.length - 1]); | |
const reconstructed = []; | |
for (let x = 0, y; x < encoded.length;) { | |
const ch = encoded[x]; | |
for (y = x; encoded[y] === ch; y++) { | |
} | |
const count = y - x; | |
if (count === 1) { | |
if (ch === '{') { | |
reconstructed.push('0'); | |
} else if (ch === '}') { | |
reconstructed.push('1'); | |
} else { | |
reconstructed.push(ch); | |
} | |
} else { | |
let left = count; | |
while (left > 0) { | |
if (left > 9) { | |
reconstructed.push(ch + 9); | |
left -= 9; | |
} else if (left === 1) { | |
reconstructed.push(ch); | |
left -= 1; | |
} else { | |
reconstructed.push(ch + left); | |
left = 0; | |
} | |
} | |
} | |
x += count; | |
} | |
const output = reconstructed.join(''); | |
if (output.length < digits) { | |
return encode(num, digits, off + 1); | |
} | |
return output; | |
} | |
function decode(encoded) { | |
const input = []; | |
encoded = encoded.split('') | |
.forEach((ch, i, inp) => { | |
if (ch.match(/^[A-Z-]+/)) { | |
input.push(ch); | |
} else if (ch === '0') { | |
input.push('{'); | |
} else if (ch === '1') { | |
input.push('}'); | |
} else { | |
let count = parseInt(ch); | |
while (count-- > 1) { | |
input.push(inp[i - 1]); | |
} | |
} | |
}); | |
const table = []; | |
for (let x = 0; x < input.length; x++) { | |
table.push(''); | |
} | |
while (table[0].length < input.length) { | |
for (let x = 0; x < input.length; x++) { | |
table[x] = input[x] + table[x]; | |
} | |
table.sort(); | |
} | |
let match = table.find(x => x.match(/^[{][^}]+[}]$/)); | |
match = match.substring(1, match.length - 1); | |
match = parseInt(match.split('').map(ch => ch === '-' ? '.' : (parseInt(ch, 36) - 10).toString(26)).join(''), 26); | |
return match; | |
} | |
for (let x = 1; x < 1e20; x *= 2) { | |
console.log(x, encode(x), decode(encode(x))); | |
} | |
console.log(nsTime, encode(nsTime), decode(encode(nsTime))); |
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