Commit d05bbf7

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algorithm: first unique char in a string (#1103)

* feat: Added Algo first unique char in a string. * Optimised algo to linear time complexity * removed double quotes * Review changes: if-else logic

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`@@ -299,6 +299,7 @@`
`299`	`299`	`* [CountVowels](String/CountVowels.js)`
`300`	`300`	`* [CreatePermutations](String/CreatePermutations.js)`
`301`	`301`	`* [DiceCoefficient](String/DiceCoefficient.js)`
	`302`	`+ * [FirstUniqueCharacter](String/FirstUniqueCharacter.js)`
`302`	`303`	`* [FormatPhoneNumber](String/FormatPhoneNumber.js)`
`303`	`304`	`* [GenerateGUID](String/GenerateGUID.js)`
`304`	`305`	`* [HammingDistance](String/HammingDistance.js)`

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	`1`	`+/**`
	`2`	`+ * @function firstUniqChar`
	`3`	`+ * @description Given a string str, find the first non-repeating character in it and return its index. If it does not exist, return -1.`
	`4`	`+ * @param {String} str - The input string`
	`5`	`+ * @return {Number} - The index of first unique character.`
	`6`	`+ * @example firstUniqChar("javascript") => 0`
	`7`	`+ * @example firstUniqChar("sesquipedalian") => 3`
	`8`	`+ * @example firstUniqChar("aabb") => -1`
	`9`	`+ */`
	`10`	`+`
	`11`	`+const firstUniqChar = (str) => {`
	`12`	`+ if (typeof str !== 'string') {`
	`13`	`+ throw new TypeError('Argument should be string')`
	`14`	`+ }`
	`15`	`+ const count = new Map()`
	`16`	`+`
	`17`	`+ for (const char of str) {`
	`18`	`+ if (!count[char]) {`
	`19`	`+ count[char] = 1`
	`20`	`+ } else {`
	`21`	`+ count[char]++`
	`22`	`+ }`
	`23`	`+ }`
	`24`	`+ for (let i = 0; i < str.length; i++) {`
	`25`	`+ if (count[str[i]] === 1) return i`
	`26`	`+ }`
	`27`	`+ return -1`
	`28`	`+}`
	`29`	`+`
	`30`	`+export { firstUniqChar }`

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	`1`	`+import { firstUniqChar } from '../FirstUniqueCharacter'`
	`2`	`+`
	`3`	`+describe('firstUniqChar', () => {`
	`4`	`+ it('locates the index of first unique character in the string', () => {`
	`5`	`+ expect(firstUniqChar('javascript')).toEqual(0)`
	`6`	`+ expect(firstUniqChar('sesquipedalian')).toEqual(3)`
	`7`	`+ expect(firstUniqChar('aabb')).toEqual(-1)`
	`8`	`+ })`
	`9`	`+})`

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