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index.ts
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index.ts
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function findNthDigit(n: number): number {
if (n < 10) {
return n;
}
if (!data.length) {
init();
}
const selected = data.find((v) => v.prev <= n && v.total > n);
// console.log(selected)
if (!selected) throw Error("accident not found");
const offset = n - selected.prev;
const current = selected.start + Math.floor(offset / selected.part);
// console.log(current)
return Number(String(current)[offset % selected.part]);
}
const data: Array<{
prev: number;
total: number;
part: number;
start: number;
end: number;
}> = [];
function init() {
let prev = 0;
let total = 10;
let part = 1;
let start = 0;
let end = 10;
while (total <= (2 ** 31 - 1) * 10) {
data.push({ prev, total: total, part: part, start, end });
part++;
start = end;
end *= 10;
prev = total;
total += part * (end - start);
}
// console.log(data)
}
export default findNthDigit;