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Row/Column Maxima, Transpose & Formatting

Find row/column maxima safely (jagged-aware) and build matrix transposes (rectangular and jagged). Practice aligned printing.

Row Maxima

Row maxima: compute the max of each row by scanning its elements once.

public class Main {
  public static void main(String[] args) {
    // Example jagged array
    int[][] m = {
      {1, 7, 3},
      {4, 9, 2, 11},
      {6}
    };

    int r = 1; // choose which row to check (row index 1 → {4, 9, 2, 11})

    // Max of a single row r
    int max = Integer.MIN_VALUE; // start with very small number
    for (int c = 0; c < m[r].length; c = c + 1) {
      if (m[r][c] > max) {
        max = m[r][c]; // update if current value is larger
      }
    }

    System.out.println("Max value in row " + r + " = " + max);
  }
}

Column Maxima

Column maxima in jagged arrays: check each row's length before reading column c.

public class Main {
  public static void main(String[] args) {
    // Example jagged array (rows with different lengths)
    int[][] m = {
      {1, 7, 3},
      {4, 9},       // shorter row (only 2 columns)
      {6, 2, 11, 5} // longer row (4 columns)
    };

    int c = 2; // column index to check (3rd column)

    // Max of column c across all rows
    int colMax = Integer.MIN_VALUE;
    for (int r = 0; r < m.length; r = r + 1) {
      // Guard: only access if this row has column c
      if (c < m[r].length) {
        if (m[r][c] > colMax) {
          colMax = m[r][c]; // update maximum
        }
      }
    }

    System.out.println("Max value in column " + c + " = " + colMax);
  }
}

All lessons in this course

  1. 2D Array Basics & Nested Iteration
  2. Jagged Arrays & Table Formatting
  3. Row/Column Maxima, Transpose & Formatting
  4. 2D Mini-Project: Gradebook
  5. 2D Utilities as a Helper Class (Refactor)
  6. 2D Data Cleaning & Validation
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