Spiral Matrix Traversal in DSA C - Practice Problems & Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of Spiral Traversal on 3x3 Matrix

What is the output of the following C code that prints the elements of a 3x3 matrix in spiral order?

DSA C

int matrix[3][3] = {{1,2,3},{4,5,6},{7,8,9}};
int i, k = 0, l = 0, m = 3, n = 3;
while (k < m && l < n) {
    for (i = l; i < n; ++i) printf("%d ", matrix[k][i]);
k++;
    for (i = k; i < m; ++i) printf("%d ", matrix[i][n-1]);
n--;
    if (k < m) {
        for (i = n-1; i >= l; --i) printf("%d ", matrix[m-1][i]);
m--;
    }
    if (l < n) {
        for (i = m-1; i >= k; --i) printf("%d ", matrix[i][l]);
l++;
    }
}

A [1, 2, 3, 6, 9, 7, 8, 4, 5]

B [1, 2, 3, 6, 9, 8, 7, 4, 5]

C [1, 2, 3, 6, 9, 8, 7, 5, 4]

D [1, 2, 3, 5, 6, 9, 8, 7, 4]

💡 Hint

Follow the spiral path: top row left to right, right column top to bottom, bottom row right to left, left column bottom to top.

The code prints the outer layer first: 1 2 3 6 9 8 7 4, then the inner element 5.

❓ Predict Output

intermediate

Spiral Traversal Output for 2x4 Matrix

What is the output of the spiral traversal for this 2x4 matrix?

DSA C

int matrix[2][4] = {{1, 2, 3, 4}, {5, 6, 7, 8}};
int i, k = 0, l = 0, m = 2, n = 4;
while (k < m && l < n) {
    for (i = l; i < n; ++i) printf("%d ", matrix[k][i]);
k++;
    for (i = k; i < m; ++i) printf("%d ", matrix[i][n-1]);
n--;
    if (k < m) {
        for (i = n-1; i >= l; --i) printf("%d ", matrix[m-1][i]);
m--;
    }
    if (l < n) {
        for (i = m-1; i >= k; --i) printf("%d ", matrix[i][l]);
l++;
    }
}

A [1, 2, 3, 4, 8, 7, 6]

B [1, 2, 3, 4, 5, 6, 7, 8]

C [1, 2, 3, 4, 8, 7, 6, 5]

D [1, 2, 3, 4, 8, 7, 5, 6]

💡 Hint

Remember to traverse the top row, then right column, then bottom row in reverse, then left column in reverse.

The spiral order is: 1 2 3 4 (top row), 8 (right column), 7 6 5 (bottom row reversed).

🔧 Debug

advanced

Identify the Bug in Spiral Traversal Code

The following code is intended to print a matrix in spiral order but produces incorrect output. What is the bug?

DSA C

int matrix[3][3] = {{1,2,3},{4,5,6},{7,8,9}};
int i, k = 0, l = 0, m = 3, n = 3;
while (k <= m && l <= n) {
    for (i = l; i < n; ++i) printf("%d ", matrix[k][i]);
k++;
    for (i = k; i < m; ++i) printf("%d ", matrix[i][n-1]);
n--;
    if (k < m) {
        for (i = n-1; i >= l; --i) printf("%d ", matrix[m-1][i]);
m--;
    }
    if (l < n) {
        for (i = m-1; i >= k; --i) printf("%d ", matrix[i][l]);
l++;
    }
}

A The matrix indices are accessed incorrectly; rows and columns are swapped.

B The inner loops should use '<=' instead of '<' for correct indexing.

C The variables m and n should be incremented inside the loop instead of decremented.

D The loop condition should be 'k < m && l < n' instead of 'k <= m && l <= n'.

💡 Hint

Check the loop condition carefully to avoid out-of-bound access.

Using '<=' causes the loops to run one extra time, leading to invalid access and wrong output.

🧠 Conceptual

advanced

Number of Layers in Spiral Traversal

For an MxN matrix, how many layers (or rings) does the spiral traversal process?

A min(M, N) / 2 rounded down

B max(M, N) / 2 rounded down

C M + N - 1

D min(M, N)

💡 Hint

Each layer removes one row and one column from each side.

Each layer covers the outer ring, so the number of layers is half the smaller dimension rounded down.

🚀 Application

expert

Spiral Traversal Output for 4x4 Matrix

What is the spiral traversal output of this 4x4 matrix?

DSA C

int matrix[4][4] = {
  {1, 2, 3, 4},
  {5, 6, 7, 8},
  {9, 10, 11, 12},
  {13, 14, 15, 16}
};
int i, k = 0, l = 0, m = 4, n = 4;
while (k < m && l < n) {
    for (i = l; i < n; ++i) printf("%d ", matrix[k][i]);
k++;
    for (i = k; i < m; ++i) printf("%d ", matrix[i][n-1]);
n--;
    if (k < m) {
        for (i = n-1; i >= l; --i) printf("%d ", matrix[m-1][i]);
m--;
    }
    if (l < n) {
        for (i = m-1; i >= k; --i) printf("%d ", matrix[i][l]);
l++;
    }
}

A [1, 2, 3, 4, 8, 12, 16, 15, 14, 13, 9, 5, 6, 7, 11, 10]

B [1, 2, 3, 4, 8, 12, 16, 15, 14, 13, 9, 5, 6, 10, 11, 7]

C [1, 2, 3, 4, 8, 12, 16, 15, 14, 13, 9, 5, 10, 11, 7, 6]

D [1, 2, 3, 4, 8, 12, 16, 15, 14, 13, 9, 5, 7, 6, 10, 11]

💡 Hint

Trace the spiral layer by layer: top row, right column, bottom row reversed, left column reversed.

The spiral order covers the outer ring first, then the inner 2x2 matrix in spiral order.