You are given a 0-indexed 2D integer matrix grid of size n * n with values in the range [1, n2]. Each integer appears exactly once except a which appears twice and b which is missing. The task is to find the repeating and missing numbers a and b. Re

findMissingAndRepeatedValues.js

/**
 * @param {number[][]} grid
 * @return {number[]}
 */
var findMissingAndRepeatedValues = function(grid) {
       const n = grid.length;
    const expectedSum = (n * n * (n * n + 1)) / 2;
    let actualSum = 0;
    const numCounts = {};
    let repeating = -1;

    // Flatten the matrix and count occurrences of each number
    for (let i = 0; i < n; i++) {
        for (let j = 0; j < n; j++) {
            const num = grid[i][j];
            actualSum += num;

            if (num in numCounts) {
                repeating = num;
            } else {
                numCounts[num] = 1;
            }
        }
    }

    // Calculate the missing number
    const missing = expectedSum - (actualSum - repeating);

    // Return the result as an array [repeating, missing]
    return [repeating, missing];
};