52 lines
1.5 KiB
JavaScript
52 lines
1.5 KiB
JavaScript
const bigInt = require('big-integer');
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const cache = new Map();
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function rev(bi) {
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const s = bi.toString().split('').reverse().join('');
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return bigInt(s);
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}
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function lychrel(n) {
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if (cache.has(n.toString())) { // bigInt 是对象，需要用字符串作为 Map 的键
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return cache.get(n.toString());
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}
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let r = rev(n);
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let res = { flag: true, bi: n };
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const seen = [];
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for (let i = 0; i < 500; i++) {
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n = n.add(r);
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r = rev(n);
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if (n.equals(r)) {
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res = { flag: false, bi: bigInt(0) };
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break;
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}
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if (cache.has(n.toString())) {
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res = cache.get(n.toString());
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break;
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}
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seen.push(n);
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}
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for (const bi of seen) {
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cache.set(bi.toString(), res);
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}
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return res;
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}
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const seeds = [];
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const related = [];
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const palin = [];
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for (let i = 1; i <= 10000; i++) {
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const n = bigInt(i);
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const t = lychrel(n);
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if (!t.flag) {
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continue;
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}
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if (n.equals(t.bi)) {
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seeds.push(t.bi);
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} else {
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related.push(t.bi);
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}
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if (n.equals(t.bi)) {
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palin.push(t.bi);
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}
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}
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console.log(`${seeds.length} Lychrel seeds: [${seeds.map(s => s.toString()).join(', ')}]`);
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console.log(`${related.length} Lychrel related`);
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console.log(`${palin.length} Lychrel palindromes: [${palin.map(p => p.toString()).join(', ')}]`);
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