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Commit 091c879

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Sandy
authored
Merge pull request #7 from openset/develop
Add: README
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## 14. Longest Common Prefix
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Write a function to find the longest common prefix string amongst an array of strings.
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If there is no common prefix, return an empty string "".
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**Example 1:**
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```text
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Input: ["flower","flow","flight"]
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Output: "fl"
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```
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**Example 2:**
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```text
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Input: ["dog","racecar","car"]
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Output: ""
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Explanation: There is no common prefix among the input strings.
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```
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**Note:**
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All given inputs are in lowercase letters `a-z`.
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## 21. Merge Two Sorted Lists
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Merge two sorted linked lists and return it as a new list. The new list should be made by splicing together the nodes of the first two lists.
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**Example:**
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```text
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Input: 1->2->4, 1->3->4
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Output: 1->1->2->3->4->4
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```

‎solution/palindrome-number/README.md

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## 9. Palindrome Number
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Determine whether an integer is a palindrome. An integer is a palindrome when it reads the same backward as forward.
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**Example 1:**
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```text
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Input: 121
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Output: true
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```
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**Example 2:**
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```text
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Input: -121
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Output: false
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Explanation: From left to right, it reads -121. From right to left, it becomes 121-. Therefore it is not a palindrome.
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```
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**Example 3:**
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```text
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Input: 10
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Output: false
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Explanation: Reads 01 from right to left. Therefore it is not a palindrome.
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```
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**Follow up:**
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Coud you solve it without converting the integer to a string?
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## 26. Remove Duplicates from Sorted Array
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Given a sorted array nums, remove the duplicates `in-place` such that each element appear only once and return the new length.
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Do not allocate extra space for another array, you must do this by `modifying the input array` `in-place` with O(1) extra memory.
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**Example 1:**
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```text
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Given nums = [1,1,2],
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Your function should return length = 2, with the first two elements of nums being 1 and 2 respectively.
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It doesn't matter what you leave beyond the returned length.
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```
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**Example 2:**
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```text
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Given nums = [0,0,1,1,1,2,2,3,3,4],
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Your function should return length = 5, with the first five elements of nums being modified to 0, 1, 2, 3, and 4 respectively.
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It doesn't matter what values are set beyond the returned length.
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```
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**Clarification:**
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Confused why the returned value is an integer but your answer is an array?
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Note that the input array is passed in by reference, which means modification to the input array will be known to the caller as well.
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Internally you can think of this:
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```text
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// nums is passed in by reference. (i.e., without making a copy)
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int len = removeDuplicates(nums);
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// any modification to nums in your function would be known by the caller.
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// using the length returned by your function, it prints the first len elements.
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for (int i = 0; i < len; i++) {
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print(nums[i]);
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}
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```

‎solution/remove-element/README.md

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The order of elements can be changed. It doesn't matter what you leave beyond the new length.
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**Example 1:**
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```
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```text
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Given nums = [3,2,2,3], val = 3,
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Your function should return length = 2, with the first two elements of nums being 2.
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It doesn't matter what you leave beyond the returned length.
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```
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**Example 2:**
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```
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**Example 2:**
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```text
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Given nums = [0,1,2,2,3,0,4,2], val = 2,
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Your function should return length = 5, with the first five elements of nums containing 0, 1, 3, 0, and 4.
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It doesn't matter what values are set beyond the returned length.
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```
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**Clarification:**
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Confused why the returned value is an integer but your answer is an array?
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Internally you can think of this:
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```
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```text
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// nums is passed in by reference. (i.e., without making a copy)
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int len = removeElement(nums, val);
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‎solution/reverse-integer/README.md

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## 7. Reverse Integer
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Given a 32-bit signed integer, reverse digits of an integer.
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**Example 1:**
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```text
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Input: 123
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Output: 321
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```
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**Example 2:**
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```text
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Input: -123
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Output: -321
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```
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**Example 3:**
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```text
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Input: 120
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Output: 21
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```
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**Note:**
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Assume we are dealing with an environment which could only store integers within the 32-bit signed integer range: [−231, 231 − 1]. For the purpose of this problem, assume that your function returns 0 when the reversed integer overflows.

‎solution/roman-to-integer/README.md

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## 13. Roman to Integer
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Roman numerals are represented by seven different symbols: `I`, `V`, `X`, `L`, `C`, `D` and `M`.
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```text
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Symbol Value
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I 1
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V 5
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X 10
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L 50
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C 100
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D 500
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M 1000
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```
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For example, two is written as `II` in Roman numeral, just two one's added together. Twelve is written as, `XII`, which is simply `X` + `II`. The number twenty seven is written as `XXVII`, which is `XX` + `V` + `II`.
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Roman numerals are usually written largest to smallest from left to right. However, the numeral for four is not `IIII`. Instead, the number four is written as `IV`. Because the one is before the five we subtract it making four. The same principle applies to the number nine, which is written as `IX`. There are six instances where subtraction is used:
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- `I` can be placed before `V` (5) and `X` (10) to make 4 and 9.
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- `X` can be placed before `L` (50) and `C` (100) to make 40 and 90.
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- `C` can be placed before `D` (500) and `M` (1000) to make 400 and 900.
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Given a roman numeral, convert it to an integer. Input is guaranteed to be within the range from 1 to 3999.
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**Example 1:**
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```text
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Input: "III"
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Output: 3
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```
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**Example 2:**
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```text
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Input: "IV"
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Output: 4
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```
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**Example 3:**
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```text
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Input: "IX"
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Output: 9
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```
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**Example 4:**
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```text
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Input: "LVIII"
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Output: 58
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Explanation: L = 50, V= 5, III = 3.
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```
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**Example 5:**
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```text
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Input: "MCMXCIV"
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Output: 1994
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Explanation: M = 1000, CM = 900, XC = 90 and IV = 4.
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```
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## 8. String to Integer (atoi)
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Implement `atoi` which converts a string to an integer.
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The function first discards as many whitespace characters as necessary until the first non-whitespace character is found. Then, starting from this character, takes an optional initial plus or minus sign followed by as many numerical digits as possible, and interprets them as a numerical value.
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The string can contain additional characters after those that form the integral number, which are ignored and have no effect on the behavior of this function.
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If the first sequence of non-whitespace characters in str is not a valid integral number, or if no such sequence exists because either str is empty or it contains only whitespace characters, no conversion is performed.
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If no valid conversion could be performed, a zero value is returned.
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**Note:**
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- Only the space character ' ' is considered as whitespace character.
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- Assume we are dealing with an environment which could only store integers within the 32-bit signed integer range: [−231, 231 − 1]. If the numerical value is out of the range of representable values, INT_MAX (231 − 1) or INT_MIN (−231) is returned.
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**Example 1:**
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```text
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Input: "42"
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Output: 42
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```
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**Example 2:**
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```text
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Input: " -42"
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Output: -42
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Explanation: The first non-whitespace character is '-', which is the minus sign.
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Then take as many numerical digits as possible, which gets 42.
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```
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**Example 3:**
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```text
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Input: "4193 with words"
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Output: 4193
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Explanation: Conversion stops at digit '3' as the next character is not a numerical digit.
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```
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**Example 4:**
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```text
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Input: "words and 987"
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Output: 0
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Explanation: The first non-whitespace character is 'w', which is not a numerical
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digit or a +/- sign. Therefore no valid conversion could be performed.
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```
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**Example 5:**
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```text
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Input: "-91283472332"
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Output: -2147483648
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Explanation: The number "-91283472332" is out of the range of a 32-bit signed integer.
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Thefore INT_MIN (−231) is returned.
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```

‎solution/two-sum/README.md

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## 1. Two Sum
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Given an array of integers, return `indices` of the two numbers such that they add up to a specific 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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**Example:**
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```text
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Given nums = [2, 7, 11, 15], target = 9,
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Because nums[0] + nums[1] = 2 + 7 = 9,
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return [0, 1].
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```

‎solution/valid-parentheses/README.md

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## 20. Valid Parentheses
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Given a string containing just the characters `'('`, `')'`, `'{'`, `'}'`, `'['` and `']'`, determine if the input string is valid.
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An input string is valid if:
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1. Open brackets must be closed by the same type of brackets.
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1. Open brackets must be closed in the correct order.
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Note that an empty string is also considered valid.
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**Example 1:**
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```text
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Input: "()"
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Output: true
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```
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**Example 2:**
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```text
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Input: "()[]{}"
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Output: true
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```
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**Example 3:**
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```text
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Input: "(]"
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Output: false
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```
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**Example 4:**
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```text
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Input: "([)]"
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Output: false
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```
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**Example 5:**
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```text
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Input: "{[]}"
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Output: true
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```

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