Created
March 15, 2026 19:52
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Permutation sequence
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| const startingN = 0 | |
| let n = startingN; | |
| const endingN = 11 | |
| type Permutation = number[]; | |
| const sequences = [] | |
| const memo: Record<string,Permutation[]> = {} | |
| const permutationPatternsForN: Permutation[][] = [] | |
| function applyPermutationPattern (numbers: number[]) { | |
| const numbersMapping: number[] = []; | |
| numbers.forEach((number:number, index:number) => { | |
| numbersMapping[number] = index | |
| }) | |
| const memoisedPermutationPattern = permutationPatternsForN[numbers.length - 1]; | |
| return memoisedPermutationPattern.map(permutation => permutation.map(number => numbers[number])) | |
| } | |
| function permuteNewInner (numbers: number[]): Permutation[] { | |
| if (numbers.length === 1) return [numbers]; | |
| if (numbers.length === 2) return [numbers, [numbers[1], numbers[0]]]; | |
| const permutations = numbers.flatMap((number: number, index:number) => { | |
| const numbersClone = [...numbers]; | |
| numbersClone.splice(index, 1); | |
| return applyPermutationPattern(numbersClone).map(p => [number, ...p]) | |
| }) | |
| return permutations | |
| } | |
| function permuteNew (numbers: number[]): Permutation[] { | |
| const permutations: Permutation[] = permuteNewInner(numbers); | |
| permutationPatternsForN.push(permutations) | |
| return permutations; | |
| } | |
| const permutations: Permutation[] = [] | |
| while (n < endingN) { | |
| permuteNew( | |
| [...Array(n+1 - startingN)].map((_, i) => i + startingN) | |
| ) | |
| .map(p => console.log(Number(p.join('')))) | |
| n++; | |
| } | |
| // permutations.map(console.log) |
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