Leetcode 41 First Missing Positive Solution in c++ | Hindi Coding Community

 

Given an unsorted integer array nums, return the smallest missing positive integer.

You must implement an algorithm that runs in O(n) time and uses constant extra space.

 

Example 1:

Input: nums = [1,2,0]

Output: 3

Explanation: The numbers in the range [1,2] are all in the array.

class Solution

{

public:

int firstMissingPositive(int A[], int n)

{

for(int i = 0; i < n; ++ i)

while(A[i] > 0 && A[i] <= n && A[A[i] - 1] != A[i])

swap(A[i], A[A[i] - 1]);

for(int i = 0; i < n; ++ i)

if(A[i] != i + 1)

return i + 1;

return n + 1;

}

};