String - JavaScript Problems

Problems relate to string.

Github: JavaScript Problems by Mitchell.

All the following code blocks use TypeScript.

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Alphanumericals

Determine if a character an alphanumerical.

Solutions

Use regular expression to match pattern.

Code

function isAlphaNumeric(char: any): Boolean {
  return /[A-Za-z0-9]/.test(char);
}

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Compare Version Numbers

Given two version strings, version1 and version2, compare them. A version string consists of revisions separated by dots '.'. The value of the revision is its integer conversion ignoring leading zeros.

To compare version strings, compare their revision values in left-to-right order. If one of the version strings has fewer revisions, treat the missing revision values as 0.

Return the following:

• If version1 < version2, return -1.

• If version1 > version2, return 1.

• Otherwise, return 0.

-LeetCode

Solutions

Use `split()` to split the string into array. Compare each char in the array.

Code

const compareVersion = function (version1: string, version2: string): number {
  const v1Arr = version1.split('.');
  const v2Arr = version2.split('.');
  const maxLen = Math.max(v1Arr.length, v2Arr.length);

  for (let i = 0; i < maxLen; i++) {
    const v1Char = parseInt(v1Arr[i]) || 0;
    const v2Char = parseInt(v2Arr[i]) || 0;
    if (v1Char > v2Char) {
      return 1;
    } else if (v1Char < v2Char) {
      return -1;
    } else {
      continue;
    }
  }

  return 0;
}

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Version Numbers Sortings

Sorting a given array of version numbers.

Solutions

The solution is similar to Compare Version Numbers.

Code

const versionSorting = function (versionArr: string[]): string[] {
  versionArr.sort((a, b) => {
    const arr1 = a.split('.');
    const arr2 = b.split('.');

    let i = 0;
    while (true) {
      const s1: number = parseInt(arr1[i]);
      const s2: number = parseInt(arr2[i]);
      i++;
      if (s1 === undefined || s2 === undefined) {
        return arr2.length - arr1.length;
      }
      if (s1 === s2) {
        continue;
      }

      return s2 - s1;
    }
  });

  return versionArr;
}

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most frequently occurring character

Given a non-empty string, return the most frequently ocurring character.

If there are multiple characters with same occurrance, return an array of them. - BFE

Solutions

Use a `Map()` to record the frequency of each character.

Code

const count = function (str: string): string | string[] {
  const map = new Map();
  const result: string[] = [];

  for (const char of str) {
    map.set(char, (map.get(char) || 0) + 1);
  }

  const max = Math.max(...map.values());

  for (const [key, value] of map) {
    if (value === max) {
      result.push(key);
    }
  }

  return result.length === 1 ? result[0] : result;
}

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Find Longest Word Length

Find the longest word length in a string.

Solutions

Use `split(‘ ‘)` to split the string and find the longest word length.

Code

const longestLength = function (str: string): number {
  return Math.max(
    ...str
      .split(' ')
      .map(x => x.length)
  );
}

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Find Word With Longest Length

Find the word with longest length in a string.

Solutions

First find the max length of the words in string. Then match the word with longest length.

Code

const longestWord = function (str: string): string[] {
  const wordArr = str.split(' ');
  const result: string[] = [];
  let max = 0;

  for (const word of wordArr) {
    if (word.length > max) {
      max = word.length;
    }
  }

  for (const word of wordArr) {
    if (word.length === max) {
      result.push(word);
    }
  }

  return result;
}

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Reference

• Alphanumericals - Wikipedia

• LeetCode 165. Compare Version Numbers

• Software versioning - Wikipedia

• BFE 145. most frequently occurring character

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