Consider the following code segment. int[][] mat = new int[4][6]; for (int r = 0; r

Question

Consider the following code segment.

int[][] mat = new int[4][6];
for (int r = 0; r < 4; r++) 
{
  for (int c = 0; c < 6; c++) 
  {
    if(c < 3 - r || c > 3 + r) 
    {
      mat[r][c] = 0;
    } 
    else 
    {
      mat[r][c] = 1;
    }
  }
}

Which of the following represents mat after this code segment is executed?

BlackTom AI · Accepted Answer

The condition c < 3 - r || c > 3 + r sets mat[r][c] to 0 when c is strictly outside the inclusive interval [3 - r, 3 + r]; otherwise mat[r][c] = 1. Key concepts: 2D array indexing (r = 0..3, c = 0..5) and interpreting compound inequalities to find the range of column indices that become 1 for each row.

Step-by-step reasoning for each row r:

- r = 0:
  - Range for ones is 3 - r .. 3 + r = 3 .. 3.
  - Valid c indices 0..5: only c = 3 is within [3,3].
  - Row 0: 0 0 0 1 0 0

- r = 1:
  - Range: 3 - 1 .. 3 + 1 = 2 .. 4.
  - c = 2,3,4 are ones; others zeros.
  - Row 1: 0 0 1 1 1 0

- r = 2:
  - Range: 3 - 2 .. 3 + 2 = 1 .. 5.
  - c = 1,2,3,4,5 are ones (c max is 5 in array).
  - Row 2: 0 1 1 1 1 1

- r = 3:
  - Range: 3 - 3 .. 3 + 3 = 0 .. 6.
  - Valid c indices are 0..5, so all columns c = 0..5 are within [0,6].
  - Row 3: 1 1 1 1 1 1

Putting the rows together (columns separated by tabs for clarity):
0	0	0	1	0	0
0	0	1	1	1	0
0	1	1	1	1	1
1	1	1	1	1	1

Why this is correct: the inequality directly determines the inclusive span of columns that become 1 for each row; as r increases the span widens symmetrically about column index 3 until the row is all ones.

Why other possible patterns would be wrong: any alternative would either miscompute the interval endpoints (e.g., using 3 ± r incorrectly), ignore array bounds (c ≤ 5), or invert the condition (placing ones outside the interval). None of those match the loop logic shown.

Final confirmation: the computed matrix matches the provided correct answer exactly.

Consider the following code segment. int[][] mat = new int[4][6]; for (int r = 0; r < 4; r++) { for (int c = 0; c < 6; c++) { if(c < 3 - r || c > 3 + r) { mat[r][c] = 0; } else { mat[r][c] = 1; } } } Which of the following represents mat after this code segment is executed?单项选择题

类似问题

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