Set Mismatch Problem Statement

You have a set of positive integers, which originally contains all the numbers from 1 to n. Unfortunately, due to some error, one of the numbers in the set got duplicated to another number in the set, which results in repetition of one number and loss of another number.

Given an integer array numbers representing the data status of this set after the error, find the number that occurs twice and the number that is missing and return them in the form of an array.

Example One

{
"numbers": [5, 4, 2, 3, 5]
}

Output:

[5, 1]

Example Two

{
"nums": [1, 1]
}

Output:

[1, 2]

Notes

Return two integers in form of a list [x, y] where x represents the duplicated number and y represents the missing number.

Constraints:

• 2 <= size of the input list <= 10⁵
• 1 <= any element of the input list <= 10⁵

Code For Set Mismatch Solution: Iterative

/*
Asymptotic complexity in terms of the number of elements in `numbers` `n`:
* Time: O(n).
* Auxiliary space: O(1).
* Total space: O(1).
*/

vector<int> find_error(vector<int> &numbers) {
    vector<int> answer(2);

    for (int i : numbers) {
        if (numbers[abs(i) - 1] < 0) {
            answer[0] = abs(i);
        }
        else {
            numbers[abs(i) - 1] *= -1;
        }
    }

    for (int i = 0; i < int(numbers.size()); i++) {
        if (numbers[i] > 0) {
            answer[1] = i + 1;
        }
    }

    return answer;
}

We hope that these solutions to the set mismatched problem have helped you level up your coding skills. You can expect problems like these at top tech companies like Amazon and Google.

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