Given a m * n matrix of distinct numbers, we have to return all lucky numbers in the 2-D array (matrix) in any order.
A lucky number is an element of the matrix such that it is the minimum element in its row and maximum in its column.
For example − If the input array is −
const arr = [ [3,7,8], [9,11,13], [15,16,17] ];
Then the output should be −
const output = [15];
because 15 is the only lucky number since it is the minimum in its row and the maximum in its column.
Example
The code for this will be −
const arr = [
[3,7,8],
[9,11,13],
[15,16,17]
];
const luckyNumbers = (arr, res = []) => {
let M = arr.length, N = arr[0].length;
let min = Array(M).fill( Infinity);
let max = Array(N).fill(-Infinity);
for (let i = 0; i < M; ++i)
for (let j = 0; j < N; ++j)
min[i] = Math.min(min[i], arr[i][j]),
max[j] = Math.max(max[j], arr[i][j]);
for (let i = 0; i < M; ++i)
for (let j = 0; j < N; ++j)
if (min[i] == max[j])
res.push(arr[i][j]);
return res;
};
console.log(luckyNumbers(arr));Output
And the output in the console will be −
[15]