First Missing Positive
You are given an array 'ARR' of integers of length N. Your task is to find the first missing positive integer in linear time and constant space. In other words, find the lowest positive integer that does not exist in the array. The array can have negative numbers as well.
For example, the input [3, 4, -1, 1] should give output 2 because it is the smallest positive number that is missing in the input array.
Input format:
The first line of input contains a single integer T, representing the number of test cases or queries to be run.
Then the T test cases follow.
The first line of each test case contains a positive integer N which represents the length of the array.
The second line of each test case contains N integers representing the elements of the array 'ARR'.
Output Format :
For each test case, print a single integer denoting the minimum positive integer that is missing from the given input array.
Th output of each test case will be printed in a separate line.
Note:
You do not need to print anything. It has already been taken care of. Just implement the given function.
Constraint :
1 <= T <= 10
1 <= N <= 10^5
-10^5 <= ARR[i] <= 10^5
Time Limit: 1 sec
AnswerBot
1y
The task is to find the lowest positive integer that does not exist in the given array of integers.
Iterate through the array and mark the positive integers as visited using the array indices.
Iterate t...read more
CodingNinjas
author
2y
Searching
- Since we are given an integer ‘N’, there could be a maximum of ‘N’ positive integers in the array.
- The minimum positive number is 1, hence we can search from 1 to N in the array.
- Run a loop fro...read more
CodingNinjas
author
2y
Sorting
- Sort the array.
- Initialize a variable counter with 1, that will keep track of the positive integers that are present in the array.
- Traverse the whole array and if the current element is negative ...read more
CodingNinjas
author
2y
Store the elements
- With the help of extra space, we can mark all the positive elements present in the array.
- Traverse the array and store all the positive elements between 0 to N+1 of the array in the v...read more
CodingNinjas
author
2y
Segregation
- Call a function that will segregate the positive integer to the negative integers i.e move all non-positive elements to the right side, and return the index at which non-positive integers S...read more
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