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75 lines
1.6 KiB
Markdown
75 lines
1.6 KiB
Markdown
---
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id: 69cfca90e8a0a6d4d6871c54
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title: "Challenge 270: Longest Common Substring"
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challengeType: 28
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dashedName: challenge-270
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---
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# --description--
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Given a string, return the longest substring that appears more than once.
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- The substrings can overlap.
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# --hints--
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`getLongestSubstring("abracadabra")` should return `"abra"`.
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```js
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assert.equal(getLongestSubstring("abracadabra"), "abra");
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```
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`getLongestSubstring("hello world hello")` should return `"hello"`.
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```js
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assert.equal(getLongestSubstring("hello world hello"), "hello");
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```
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`getLongestSubstring("mississippi")` should return `"issi"`.
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```js
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assert.equal(getLongestSubstring("mississippi"), "issi");
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```
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`getLongestSubstring("ha ha ha ha ha ha ha")` should return `"ha ha ha ha ha ha"`.
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```js
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assert.equal(getLongestSubstring("ha ha ha ha ha ha ha"), "ha ha ha ha ha ha");
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```
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`getLongestSubstring("the quick brown fox jumped over the lazy dog that the quick brown fox jumped over")` should return `"the quick brown fox jumped over"`.
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```js
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assert.equal(getLongestSubstring("the quick brown fox jumped over the lazy dog that the quick brown fox jumped over"), "the quick brown fox jumped over");
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```
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# --seed--
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## --seed-contents--
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```js
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function getLongestSubstring(str) {
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return str;
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}
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```
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# --solutions--
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```js
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function getLongestSubstring(str) {
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let longest = '';
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for (let len = str.length - 1; len >= 1; len--) {
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for (let i = 0; i <= str.length - len; i++) {
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const sub = str.slice(i, i + len);
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if (str.indexOf(sub) !== str.lastIndexOf(sub)) {
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return sub;
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}
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}
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}
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return longest;
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}
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```
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