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Updating tests and proof solution for palindrome-products
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114 changes: 32 additions & 82 deletions
114
exercises/practice/palindrome-products/.meta/proof.ci.js
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -1,88 +1,38 @@ | ||
| const reverseString = (str) => str.split('').reverse().join(''); | ||
|
|
||
| class Palindrome { | ||
| constructor(factor1, factor2) { | ||
| this.value = factor1 * factor2; | ||
| this.factors = [[factor1, factor2]]; | ||
| } | ||
|
|
||
| withFactors(factors) { | ||
| this.factors.push(factors); | ||
| return this; | ||
| } | ||
|
|
||
| valid() { | ||
| const s = `${this.value}`; | ||
| return s === reverseString(s); | ||
| } | ||
|
|
||
| merge(other) { | ||
| other.factors.forEach((f) => { | ||
| this.factors.push(f); | ||
| }); | ||
| return this; | ||
| } | ||
| } | ||
|
|
||
| export class Palindromes { | ||
| constructor(maxFactor, minFactor = 1) { | ||
| this.maxFactor = maxFactor; | ||
| this.minFactor = minFactor; | ||
| } | ||
|
|
||
| get largest() { | ||
| let left = this.maxFactor, | ||
| right = this.maxFactor, | ||
| best = new Palindrome(this.minFactor, this.minFactor); | ||
|
|
||
| while (right >= this.minFactor) { | ||
| let p = new Palindrome(left, right); | ||
|
|
||
| if (best.value && p.value < best.value) { | ||
| right--; | ||
| left = right; | ||
| continue; | ||
| } | ||
|
|
||
| if (p.valid()) { | ||
| if (best.value < p.value) { | ||
| best = p; | ||
| } else if (best.value === p.value) { | ||
| best = p.merge(best); | ||
| static generate({ minFactor, maxFactor }) { | ||
| if (minFactor > maxFactor) throw new Error('min must be <= max'); | ||
| let isPalindrome = (n) => | ||
| [...n.toString()].reverse().join('') === n.toString(); | ||
| let search = (n, pred, fn) => { | ||
| while (pred(n)) { | ||
| if (!isPalindrome(n)) { | ||
| n = fn(n); | ||
| continue; | ||
| } | ||
| } | ||
|
|
||
| if (left <= this.minFactor) { | ||
| right--; | ||
| left = right; | ||
| } else { | ||
| left--; | ||
| } | ||
| } | ||
|
|
||
| if (best.valid()) { | ||
| return best; | ||
| } | ||
|
|
||
| return { value: null, factors: [] }; | ||
| } | ||
|
|
||
| get smallest() { | ||
| for (let m = this.minFactor; m <= this.maxFactor; m += 1) { | ||
| for (let n = m; n <= this.maxFactor; n += 1) { | ||
| const p = new Palindrome(m, n); | ||
| if (p.valid()) { | ||
| return p; | ||
| let factors = []; | ||
| for (let p = minFactor; p <= n / p; p++) { | ||
| if (n % p === 0) { | ||
| let q = n / p; | ||
| if (q <= maxFactor) factors.push([p, q]); | ||
| } | ||
| } | ||
| if (factors.length > 0) return { value: n, factors }; | ||
| n = fn(n); | ||
| } | ||
| } | ||
| return { value: null, factors: [] }; | ||
| } | ||
|
|
||
| static generate(params) { | ||
| if ((params.minFactor || 1) > params.maxFactor) { | ||
| throw new Error('min must be <= max'); | ||
| } | ||
| return new Palindromes(params.maxFactor, params.minFactor || 1); | ||
| return { value: null, factors: [] }; | ||
| }; | ||
| let [lower, upper] = [minFactor * minFactor, maxFactor * maxFactor]; | ||
| return { | ||
| largest: search( | ||
| upper, | ||
| (n) => n >= lower, | ||
| (x) => x - 1, | ||
| ), | ||
| smallest: search( | ||
| lower, | ||
| (n) => n <= upper, | ||
| (x) => x + 1, | ||
| ), | ||
| }; | ||
| } | ||
| } |
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