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How to find the minimum element of each row in a matrix

abhilash

Problem overview

Given a m x n matrix, find the minimum element of each row in the matrix.

Example:

Matrix:

[[12, 43],
[234, 54],
[642, 687],
[23, 99]]

Result:

[12, 54, 642, 23]

Algorithm

Every row in a matrix is an array. Hence, we need to find the minimum element of an array.

The steps of the algorithm are as follows:

  • For every row in the matrix, perform the following steps:
    • Initially, the first element will be considered the minimum element. The first element will be set as min, and then the row will be traversed.
    • Each element will be compared with the min, and if the current element is lesser than the min, the min will be set to the current element.
    • Finally, the min for the row is returned.
  • Collect all the minimums from the previous step to an array.
    • Time Complexity: O(m*n)
    • Space Complexity: O(1)

Code

import java.util.Arrays;

public class Main {

    private static int minElement(int[] row){
        int min = row[0];
        for (int i : row) min = Math.min(min, i);
        return min;
    }

    private static int[] minElementRow(int[][] matrix) {
        int[] rowMinElements = new int[matrix.length];
        int i = 0;
        for(int[] row: matrix) {
            rowMinElements[i] = minElement(row);
            i++;
        }
        return rowMinElements;
    }

    public static void main(String[] args) {
        int[][] matrix = { {12, 43},
                {234, 54},
                {642, 687},
                {23, 99}
        };
        int[] maxElements = minElementRow(matrix);
        System.out.println("Minimum elements in each row are as follows: ");
        System.out.println(Arrays.toString(maxElements));
    }
}

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