Merge pull request #520 from sir-gon/feature/sherlock-and-valid-string

[Hacker Rank] Interview Preparation Kit: String Manipulation: Sherloc…

Author: sir-gon

docs/hackerrank/interview_preparation_kit/string_manipulation/sherlock-and-valid-string.md

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+# [String Manipulation: Sherlock and the Valid String](https://www.hackerrank.com/challenges/sherlock-and-valid-string)
+
+- Difficulty:  `#medium`
+- Category: `#ProblemSolvinIntermediate` `#strings`
+
+Sherlock considers a string to be valid if all characters of the string appear
+the same number of times.
+It is also valid if he can remove just ´1´ character at  index in the string,
+and the remaining characters will occur the same number of times.
+Given a string `s`, determine if it is valid.
+If so, return `YES`, otherwise return `NO`.
+
+## Example
+
+`s = abc`
+
+This is a valid string because frequencies are `{a: 1, b: 1, c: 1}`.
+
+`s = abcc`
+
+This is a valid string because we can remove one `c` and have  of
+each character in the remaining string.
+
+`s = abccc`
+
+This string is not valid as we can only remove `1` occurrence of `c`.
+That leaves character frequencies of `{a: 1, b: 1, c: 2}`.
+
+## Function Description
+
+Complete the isValid function in the editor below.
+
+isValid has the following parameter(s):
+
+- `string s`: a string
+
+## Returns
+
+- `string`: either `YES` or `NO`
+
+## Input Format
+
+A single string `s`.
+
+## Constraints
+
+- $ 1 \leq |s| \leq 10^5  $
+- Each character `s[i]` $ \in $ `ascii[a-z]`
+
+## Sample Input 0
+
+```text
+aabbcd
+```
+
+## Sample Output 0
+
+```text
+NO
+```
+
+## Explanation 0
+
+Given `s = "abbcd"`, we would need to remove two characters,
+both `c` and `d` -> `aabb` or a and b  abcd, to make it valid.
+We are limited to removing only one character, so `s` is invalid.
+
+## Sample Input 1
+
+```text
+aabbccddeefghi
+```
+
+## Sample Output 1
+
+```text
+NO
+```
+
+## Explanation 1
+
+Frequency counts for the letters are as follows:
+
+```text
+{'a': 2, 'b': 2, 'c': 2, 'd': 2, 'e': 2, 'f': 1, 'g': 1, 'h': 1, 'i': 1}
+```
+
+There are two ways to make the valid string:
+
+- Remove `4` characters with a frequency of `1`: `{fghi}`.
+- Remove `5` characters of frequency `2`: `{abcde}`.
+Neither of these is an option.
+
+## Sample Input 2
+
+```text
+abcdefghhgfedecba
+```
+
+## Sample Output 2
+
+```text
+YES
+```
+
+## Explanation 2
+
+All characters occur twice except for `e`  which occurs `3` times.
+We can delete one instance of `e` to have a valid string.

src/hackerrank/interview_preparation_kit/string_manipulation/sherlock_and_valid_string.js

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+/**
+ * @link Problem definition [[docs/hackerrank/interview_preparation_kit/string_manipulation/sherlock-and-valid-string.md]]
+ */
+
+const __YES__ = 'YES';
+const __NO__ = 'NO';
+
+export function isValidCompute(s) {
+  if (s.length <= 1) {
+    return true;
+  }
+
+  const stringMap = {};
+
+  for (const letter of s.split('')) {
+    stringMap[letter] = stringMap?.[letter] ? stringMap[letter] + 1 : 1;
+  }
+
+  const frequencies = {};
+
+  for (const event of Object.values(stringMap)) {
+    frequencies[event] = frequencies?.[event] ? frequencies[event] + 1 : 1;
+  }
+
+  const frequenciesSize = Object.entries(frequencies).length;
+
+  if (frequenciesSize === 1) {
+    return true;
+  }
+
+  if (frequenciesSize === 2) {
+    const frequenciesList = Object.entries(frequencies).sort(
+      ([, a], [, b]) => a - b
+    );
+    const __RADIX__ = 10;
+    const __TOLERANCE__ = 1;
+    const minorFreq = parseInt(frequenciesList[0][0], __RADIX__);
+    const majorFreq = parseInt(frequenciesList[1][0], __RADIX__);
+
+    if (
+      frequencies[minorFreq] === __TOLERANCE__ &&
+      (minorFreq === __TOLERANCE__ || minorFreq - majorFreq === __TOLERANCE__)
+    ) {
+      return true;
+    }
+  }
+
+  return false;
+}
+
+export function isValid(s) {
+  return isValidCompute(s) ? __YES__ : __NO__;
+}
+
+export default { isValid };

src/hackerrank/interview_preparation_kit/string_manipulation/sherlock_and_valid_string.test.js

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+import { describe, expect, it } from '@jest/globals';
+
+import { isValid } from './sherlock_and_valid_string.js';
+import TEST_CASES from './sherlock_and_valid_string.testcases.json';
+
+describe('isValid', () => {
+  it('isValid test cases', () => {
+    expect.assertions(9);
+
+    const __YES__ = 'YES';
+
+    TEST_CASES.forEach((test) => {
+      const result = isValid(test.input) === __YES__;
+
+      expect(result).toStrictEqual(test.expected);
+    });
+  });
+});

src/hackerrank/interview_preparation_kit/string_manipulation/sherlock_and_valid_string.testcases.json

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+[
+  {
+    "title": "counterexample",
+    "input": "aabbccc",
+    "expected": true
+  },
+  {
+    "title": "counterexample",
+    "input": "a",
+    "expected": true
+  },
+  {
+    "title": "counterexample",
+    "input": "aaa",
+    "expected": true
+  },
+  {
+    "title": "counterexample",
+    "input": "abbccc",
+    "expected": false
+  },
+  {
+    "title": "counterexample",
+    "input": "bbccc",
+    "expected": false
+  },
+  {
+    "title": "Sample Test case 0",
+    "input": "aabbcd",
+    "expected": false
+  },
+  {
+    "title": "Sample Test case 1",
+    "input": "aabbccddeefghi",
+    "expected": false
+  },
+  {
+    "title": "Sample Test case 2",
+    "input": "abcdefghhgfedecba",
+    "expected": true
+  },
+  {
+    "title": "Sample Test case 4",
+    "input": "aabbc",
+    "expected": true
+  }
+]