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# codediodeio/longest-substring.js

Created September 4, 2017 23:13
Longest Substring JavaScript - LeetCode Solution
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 // Given a string, find the length of the longest substring without repeating characters. // Examples: // Given "abcabcbb", the answer is "abc", which the length is 3. // Given "bbbbb", the answer is "b", with the length of 1. // Given "pwwkew", the answer is "wke", with the length of 3. Note that the answer must be a substring, "pwke" is a subsequence and not a substring. var lengthOfLongestSubstring = function(s) { let map = {} let start = 0 let maxLen = 0 let arr = s.split('') for (i=0; i < s.length; i++) { let current = map[arr[i]] if (current!=null && start <= current) { start = current + 1 } else { maxLen = Math.max(maxLen, i - start + 1) } map[arr[i]] = i } return maxLen };

### salimakhtar92 commented Mar 6, 2020 • edited

``````function getLongestSubString(str) {
if(!str.trim()) {
}
const strArray = str.trim().split('');
let count = 0, maxLength = 0, index;
for(let i = 0; i<strArray.length; i++) {
if(strArray[i] === strArray[i+1]) {
count++;
} else {
if(count> maxLength) {
maxLength = count;
index=i;
}
count=0;
}
}

const subStrIndex = index - maxLength;
const subString = str.slice(subStrIndex, subStrIndex + maxLength+1)

if(subString) {
return {index: subStrIndex, length: maxLength + 1, subString: subString };
}

return "No sub-string found";
}

const str = "aabbbcd";
console.log(largestSubString(str)) // {index: 2, length: 3, subString: "bbb", }
``````

### alex-kucheryavenko commented Apr 21, 2020 • edited

``````function maxSubstring(s) {
const array = []
const lengthS = s.length
const pusher = (value) => {
if (value !== '') {
if (array.length > 0) {
if (array.indexOf(value) === -1) {
array.push(value)
}
} else {
array.push(value)
}
}
}
pusher(s)
for (const [index, value] of s.split('').entries()) {
let length = lengthS
let string = s
const indexO = s.indexOf(value)
pusher(value)
while (length > indexO) {
pusher(string.slice(index-1, length + 1))
length = --length
}
string = s.slice(index, lengthS)
}
array.sort()
return array.pop()
}

``````

### osramesh06 commented May 9, 2021

let str = "abcabcbbb";
let seen = {};
let start = 0;
let maxLength = 0;

[...str].map((itm, i) => {
if(itm in seen && start <= seen[itm]) {
start = seen[itm];
maxLength = Math.max(i - start, maxLength)
}
seen[itm] = i
})

console.log(maxLength)