AP CSA 4.13 Exercise 1: Rows, Columns, and the Biggest Value

AP CSA Hub Unit 4 4.1 â–¼ Lesson Ex 1 Ex 2 Quiz 4.2 â–¼ Lesson Ex 1 Ex 2 Quiz 4.3 â–¼ Lesson Ex 1 Ex 2 Quiz 4.4 â–¼ Lesson Ex 1 Ex 2 Quiz 4.5 â–¼ Lesson Ex 1 Ex 2 Quiz 4.6 â–¼ Lesson Ex 1 Ex 2 Quiz 4.7 â–¼ Lesson Ex 1 Ex 2 Quiz 4.8 â–¼ Lesson Ex 1 Ex 2 Quiz 4.9 â–¼ Lesson Ex 1 Ex 2 Quiz 4.10 â–¼ Lesson Ex 1 Ex 2 Quiz 4.11 â–¼ Lesson Ex 1 Ex 2 Quiz 4.12 â–¼ Lesson Ex 1 Ex 2 Quiz 4.13 â–¼ Lesson Ex 1 Ex 2 Quiz 4.14 â–¼ Lesson Ex 1 Ex 2 Quiz 4.15 â–¼ Lesson Ex 1 Ex 2 Quiz 4.16 â–¼ Lesson Ex 1 Ex 2 Quiz 4.17 â–¼ Lesson Ex 1 Ex 2 Quiz

Unit 4: Data Collections · Lesson 4.13 · Exercise 1

Rows, Columns, and the Biggest Value

Implementing 2D Array Algorithms. Write real Java, run it, and submit it to be graded against hidden test cases.

Back to the Lesson 4.13 pageAll Unit 4 lessons

Why this one is worth doing

Every 2D array algorithm is really a 1D array algorithm run once per row or once per column, plus bookkeeping about which row or column is winning. This exercise asks for both directions, the single largest value and where it sits, and a grid built by swapping which index means row and which means column.

What to write

  1. Read rows and cols, then rows times cols integers filling the grid, row by row.
  2. Print the index of the row with the largest row sum. When two rows tie, print the first one.
  3. Print the index of the column with the largest column sum. When two columns tie, print the first one.
  4. Print the largest single value anywhere in the grid, then the row and column where it FIRST appears in row major order.
  5. Build the TRANSPOSE of the grid: a new grid with cols rows and rows columns, where transposed[c][r] equals grid[r][c]. Print every value of the transpose in row major order, one per line.

Your program reads

Two integers, rows and cols, then rows times cols integers in row order.

Your program prints

The best row index, the best column index, the largest value and its row and column, then every value of the transposed grid.

Worked examples

These are the cases you can see. There are more you cannot, and they use different values, so an answer that prints these numbers as constants will fail.

Example 1 input
2 3
1 2 3
4 5 6
Example 1 output
1
2
6
1
2
1
4
2
5
3
6
Example 2 input
1 1
9
Example 2 output
0
0
9
0
0
9

Your answer

Main.java

Input for the Run button

Run sends whatever is in the input box below. Submitting runs your program against every test case, including hidden ones with different input.


  

  
Stuck?

    
Hint 1
A row or column sum needs its own running total reset to 0 before each row or column starts, or the sums bleed into each other.

    
Hint 2
Seed bestRowSum and bestColSum from index 0 rather than from 0 itself, or a grid that is entirely negative reports index 0 as never the best.

    
Hint 3
transposed[c][r] = grid[r][c] is the whole transpose: the new grid has cols rows and rows columns, and every value just changes which index it is read by.


  
Where to go next

  

    Rework the Lesson 4.13 page
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