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Commit 693a105

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mukul
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41. First Missing Positive
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/*
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41. First Missing Positive
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https://leetcode.com/problems/first-missing-positive/
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Problem:
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Given an unsorted integer array nums. Return the smallest positive integer that is not present in nums.
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You must implement an algorithm that runs in O(n) time and uses O(1) auxiliary space.
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Example 1:
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Input: nums = [1,2,0]
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Output: 3
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Explanation: The numbers in the range [1,2] are all in the array.
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Example 2:
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Input: nums = [3,4,-1,1]
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Output: 2
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Explanation: 1 is in the array but 2 is missing.
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Example 3:
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Input: nums = [7,8,9,11,12]
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Output: 1
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Explanation: The smallest positive integer 1 is missing.
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Constraints:
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1 <= nums.length <= 10^5
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-2^31 <= nums[i] <= 2^31 - 1
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Explanation
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Initialize n
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const n = nums.length;
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This line sets the variable n to the length of the input array nums. It represents the size of the array.
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This is the cyclic sort algorithm. It iterates through the array and, in each step, it checks if the current element nums[i] is within the valid range (1 to n) and not in its correct position. If so, it swaps the element with the one at its correct position.
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After the cyclic sort, this loop searches for the first element that is out of place. If nums[i] is not equal to i + 1, it means that i + 1 is the smallest missing positive integer, and it is returned.
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Return Next Positive Integer if All Elements Are in Place,
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If all elements are in their correct positions, the function returns the next positive integer after the maximum element in the array (n + 1).
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*/
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/**
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* @param {number[]} nums
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* @return {number}
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*/
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var firstMissingPositive = function(nums) {
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const n = nums.length
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for (let i = 0; i < n; i++)
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while (nums[i] > 0 && nums[i] <= n && nums[nums[i] - 1] !== nums[i])
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[nums[nums[i] - 1], nums[i]] = [nums[i], nums[nums[i] - 1]]
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for (let i = 0; i < n; i++)
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if (nums[i] !== i + 1)
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return i + 1
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return n + 1
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};
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module.exports.firstMissingPositive = firstMissingPositive;
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const assert = require("assert");
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const bitReverseToMakeNumberEqual = require("../../../LeetcodeProblems/Algorithms/hard/First_Missing_Positive").firstMissingPositive;
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function test() {
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assert.deepEqual(
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firstMissingPositive([1,2,0]),
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2
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);
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assert.deepEqual(
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firstMissingPositive([3,4,-1,1]),
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2
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);
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assert.deepEqual(
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firstMissingPositive([7,8,9,11,12]),
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1
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);
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}
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module.exports.test = test;

‎README.md

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@@ -16,6 +16,7 @@ The solutions are located under `/LeetcodeProblems`. Each problem has a test fil
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| Name | Level | Link |
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|----------------------------------------------------------------------------------------------------------------------------------------------------------------|--------|---------------------------------------------------------------------------------------------------------------------|
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| [Edit Distance ](/LeetcodeProblems/Algorithms/hard/Edit_Distance.js) | Hard | https://leetcode.com/problems/edit-distance/ |
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| [First Missing Positive ](/LeetcodeProblems/Algorithms/hard/First_Missing_Positive.js) | Hard | https://leetcode.com/problems/first-missing-positive/ |
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| [Remove Invalid Parentheses ](/LeetcodeProblems/Algorithms/hard/Remove_Invalid_Parentheses.js) | Hard | https://leetcode.com/problems/remove-invalid-parentheses/ |
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| [Longest Consecutive Sequence ](/LeetcodeProblems/Algorithms/hard/Longest_Consecutive_Sequence.js) | Hard | https://leetcode.com/problems/longest-consecutive-sequence/ |
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| [Minimum Window Substring ](/LeetcodeProblems/Algorithms/hard/Minimum_Window_Substring.js) | Hard | https://leetcode.com/problems/minimum-window-substring/ |

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