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ADVANCED DATA STRUCTURES PROGRAM • LEVEL 10 — SPARSE MATRICES

Fast-Transpose a Sparse Matrix

Learn how to fast-transpose a sparse matrix using a clear C program.

AdvancedSparse representationTriplet form

PROBLEM UNDERSTANDING

Input and expected output

Sample input
No input required
Sample output
0 1 5
1 2 6
2 0 4
2 2 7

COMPLETE C PROGRAM

Complete C implementation

ads-fast-transpose-triplet.c
Open in compiler
#include <stdio.h>

int main(void)
{
    int source[][3] = {{0, 2, 4}, {1, 0, 5}, {2, 1, 6}, {2, 2, 7}};
    int count[3] = {0}, position[3] = {0}, result[4][3];
    for (int index = 0; index < 4; index++) count[source[index][1]]++;
    for (int column = 1; column < 3; column++) position[column] = position[column - 1] + count[column - 1];
    for (int index = 0; index < 4; index++) {
        int slot = position[source[index][1]]++;
        result[slot][0] = source[index][1]; result[slot][1] = source[index][0]; result[slot][2] = source[index][2];
    }
    for (int index = 0; index < 4; index++) printf("%d %d %d\n", result[index][0], result[index][1], result[index][2]);
    return 0;
}

GUIDED CODE TOUR • NOT LIVE EXECUTION

Study the program line by line

Use the real compiler button above to run and debug with different inputs.

CURRENT STEP

Select Start to walk through the important lines.

SELECTED LINE

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EXPECTED OUTPUT FOR THE SAMPLE

0 1 5
1 2 6
2 0 4
2 2 7
0%Step 0 of 0

PROGRAM EXPLANATION

Algorithm and explanation

  1. Read the required input values.
  2. Count entries per destination row and use prefix positions to place each transposed triplet directly.
  3. Display the computed result.

Count entries per destination row and use prefix positions to place each transposed triplet directly.

EFFICIENCY

Time and space complexity

Time complexity

O(columns + non-zero)

Auxiliary space

O(non-zero elements)

DEBUGGING CHECKLIST

Common mistakes

Check this

Use the correct format specifier for every variable.

Check this

Initialize variables before using their values.

Check this

Check braces, semicolons and input order carefully.

Try it yourself

Practice: Run the program with the sample input, predict its output, and then test one boundary case of your own.