Question

How to check if a matrix columns contain numbers without repetition in C

Answer 1

#include <stdio.h>
#include <stdbool.h>

#define ROWS 3
#define COLS 3

bool columns_have_unique_numbers(int matrix[ROWS][COLS], int rows, int cols) {
    for (int j = 0; j < cols; j++) {
        bool seen[10000] = {false}; // Assuming numbers are between 0-9999

        for (int i = 0; i < rows; i++) {
            if (seen[matrix[i][j]]) {
                return false; // Duplicate found in column
            }
            seen[matrix[i][j]] = true;
        }
    }
    return true;
}

int main() {
    int matrix1[ROWS][COLS] = {
        {1, 4, 7},
        {2, 5, 8},
        {3, 6, 9}
    };

    int matrix2[ROWS][COLS] = {
        {1, 4, 7},
        {2, 4, 8},
        {3, 6, 9}
    };

    printf("Matrix 1 columns have unique numbers: %s\n",
           columns_have_unique_numbers(matrix1, ROWS, COLS) ? "true" : "false");
    printf("Matrix 2 columns have unique numbers: %s\n",
           columns_have_unique_numbers(matrix2, ROWS, COLS) ? "true" : "false");

    return 0;
}


/*
run:

Matrix 1 columns have unique numbers: true
Matrix 2 columns have unique numbers: false

*/

 

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