├── 1-two-sum ├── README.md └── two-sum.js └── 3-longest-substring-without-repeating-characters ├── README.md └── longest-substring-without-repeating-characters.js /1-two-sum/README.md: -------------------------------------------------------------------------------- 1 |

Two Sum

Given an array of integers nums and an integer target, return indices of the two numbers such that they add up to target.

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You may assume that each input would have exactly one solution, and you may not use the same element twice.

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You can return the answer in any order.

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Example 1:

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11 | Input: nums = [2,7,11,15], target = 9
12 | Output: [0,1]
13 | Explanation: Because nums[0] + nums[1] == 9, we return [0, 1].
14 |

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Example 2:

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19 | Input: nums = [3,2,4], target = 6
20 | Output: [1,2]
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Example 3:

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26 | Input: nums = [3,3], target = 6
27 | Output: [0,1]
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31 |

Constraints:

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2 <= nums.length <= 10⁴
-10⁹ <= nums[i] <= 10⁹
-10⁹ <= target <= 10⁹
Only one valid answer exists.

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41 | Follow-up: Can you come up with an algorithm that is less than O(n²) time complexity? -------------------------------------------------------------------------------- /1-two-sum/two-sum.js: -------------------------------------------------------------------------------- 1 | /** 2 | * @param {number[]} nums 3 | * @param {number} target 4 | * @return {number[]} 5 | */ 6 | var twoSum = function(nums, target) { 7 | let res = new Map(); 8 | for (let i = 0; i < nums.length; i ++) { 9 | const sub = target - nums[i]; 10 | if (res.has(sub)) return [res.get(sub), i]; 11 | res.set(nums[i], i); 12 | } 13 | return []; 14 | }; -------------------------------------------------------------------------------- /3-longest-substring-without-repeating-characters/README.md: -------------------------------------------------------------------------------- 1 |

Longest Substring Without Repeating Characters

Given a string s, find the length of the longest substring without repeating characters.

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4 |

Example 1:

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 7 | Input: s = "abcabcbb"
 8 | Output: 3
 9 | Explanation: The answer is "abc", with the length of 3.
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Example 2:

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15 | Input: s = "bbbbb"
16 | Output: 1
17 | Explanation: The answer is "b", with the length of 1.
18 |

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Example 3:

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23 | Input: s = "pwwkew"
24 | Output: 3
25 | Explanation: The answer is "wke", with the length of 3.
26 | Notice that the answer must be a substring, "pwke" is a subsequence and not a substring.
27 |

28 | 29 |

30 |

Constraints:

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0 <= s.length <= 5 * 10⁴
s consists of English letters, digits, symbols and spaces.

36 | -------------------------------------------------------------------------------- /3-longest-substring-without-repeating-characters/longest-substring-without-repeating-characters.js: -------------------------------------------------------------------------------- 1 | /** 2 | * @param {string} s 3 | * @return {number} 4 | */ 5 | var lengthOfLongestSubstring = function (s) { 6 | let chatMap = new Map(); 7 | let left = 0; 8 | let maxLen = 0; 9 | 10 | for (let right = 0; right < s.length; right ++) { 11 | const currentChar = s[right]; 12 | if (chatMap.has(currentChar) && chatMap.get(currentChar) >= left) { 13 | left = chatMap.get(currentChar) + 1; 14 | } 15 | chatMap.set(currentChar, right); 16 | maxLen = Math.max(maxLen, right - left + 1); 17 | } 18 | return maxLen; 19 | }; --------------------------------------------------------------------------------