int Solution::firstMissingPositive(vector &A)

{

int n=A.size();

int temp[n+1]={0}; //new temp array with size of the max() value of our given array, all

//initalized to 0

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

{

if(A[i] > 0 && A[i] <= n)

temp[A[i]] = 1;

}

for (int i = 1; i <= n; i++)

{

if (!temp[i])

return i; // Find the first element which didn’t appear in the original array

}

return n+1; //If the original array was of the type {1, 2, 3} in its sorted form

}

# Best and very simple C++ solution (Must check)

**shubham-code**#1