공식

union parent


var accountsMerge = function (accounts) {
    const parents = {};
    const email2name = {};

    const find = (x) => {
        if (parents[x] !== x) {
            parents[x] = find(parents[x]);
        }

        return parents[x];
    };

    const union = (x, y) => {
        console.log(y, '--', parents[y])
        parents[find(x)] = parents[y];
    };

    for (const [name, ...emails] of accounts) {
        for (const email of emails) {
            if (!parents[email]) {
                parents[email] = email;
            }

            email2name[email] = name;
            union(email, emails[0]);
        }
    }

    const emails = {};
    for (const email of Object.keys(parents)) {
        const parent = find(email);
        if (parent in emails) {
            emails[parent].push(email);
        } else {
            emails[parent] = [email];
        }
    }

    return Object.entries(emails).map(([email, x]) => [email2name[email], ...x.sort()]);
};

순열


var accountsMerge = function (accounts) {
    const parents = {};
    const email2name = {};

    const find = (x) => {
        if (parents[x] !== x) {
            parents[x] = find(parents[x]);
        }

        return parents[x];
    };

    const union = (x, y) => {
        console.log(y, '--', parents[y])
        parents[find(x)] = parents[y];
    };

    for (const [name, ...emails] of accounts) {
        for (const email of emails) {
            if (!parents[email]) {
                parents[email] = email;
            }

            email2name[email] = name;
            union(email, emails[0]);
        }
    }

    const emails = {};
    for (const email of Object.keys(parents)) {
        const parent = find(email);
        if (parent in emails) {
            emails[parent].push(email);
        } else {
            emails[parent] = [email];
        }
    }

    return Object.entries(emails).map(([email, x]) => [email2name[email], ...x.sort()]);
};

stringToInteger


const convertStringToInteger = (string) => {
  let isNegative = false;
  if (string[0] === '-') {
    isNegative = true;
    string = string.slice(1);
  }

  let result = 0;
  for (let i = 0; i < string.length; i++) {
    result = result * 10 + (string.charCodeAt(i) - 48);
  }

  return isNegative ? -result : result;
}