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## LeetCode problem 424 Longest Repeating Character Replacement(Java)

Given a string that consists of only uppercase English letters, you can replace any letter in the string with another letter at most k times. Find the length of a longest substring containing all repeating letters you can get after performing the above operations.

Note:
Both the string’s length and k will not exceed 104.

Example 1:

Input: s = “ABAB”, k = 2
Output: 4
Explanation: Replace the two ‘A’s with two ‘B’s or vice versa.

Example 2:

Input: s = “AABABBA”, k = 1
Output: 4
Explanation: Replace the one ‘A’ in the middle with ‘B’ and form “AABBBBA”. The substring “BBBB” has the longest repeating letters, which is 4.

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## LeetCode Problem 30 Substring with Concatenation of All Words (Java)

You are given a string, s, and a list of words, words, that are all of the same lengths. Find all starting indices of substring(s) in s that is a concatenation of each word in words exactly once and without any intervening characters.

Example 1:

Input: s = “barfoothefoobarman”, words = [“foo”,”bar”]
Output: `[0,9]`
Explanation: Substrings starting at index 0 and 9 are “barfoor” and “foobar” respectively. The output order does not matter, returning [9,0] is fine too.

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## LeetCode 3. Longest Substring Without Repeating Characters (Java)

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

Example 1:
Input: “abcabcbb”
Output: 3
Explanation: The answer is `"abc"`, with the length of 3.

Example 2:
Input: “bbbbb”
Output: 1
Explanation: The answer is `"b"`, with the length of 1.

Example 3:
Input: “pwwkew”
Output: 3
Explanation: 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.

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## Leetcode 2 Add Two Numbers (Java)

Medium

You are given two non-empty linked lists representing two non-negative integers. The digits are stored in reverse order and each of their nodes contains a single digit. Add the two numbers and return it as a linked list.
You may assume the two numbers do not contain any leading zero, except the number 0 itself.

Example:
Input: (2 -> 4 -> 3) + (5 -> 6 -> 4)
Output: 7 -> 0 -> 8
Explanation: 342 + 465 = 807.

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## Leetcode 1. Two Sum (Java)

Source Url: https://leetcode.com/problems/two-sum/

Easy

Given an array of integers, return indices of the two numbers such that they add up to a specific target.

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

Example:

Given nums = [2, 7, 11, 15], target = 9,
Because nums + nums = 2 + 7 = 9, return [0, 1].