Question

How to convert a 2D array to a 1D array in C

Answer 1

#include <stdio.h>
 
#define SIZE 3
 
void arr2DTo1D(int arr2d[][3], int rows, int cols, int arr[]) {
    int k = 0;
    for (int i = 0; i < rows; i++) {
        for (int j = 0; j < cols; j++) {
            arr[k++] = arr2d[i][j];
        }
    }
}
 
int main() {
    int arr2d[SIZE][SIZE] = { 
        { 5, 6, 1 }, 
        { 3, 8, 0 },
        { 9, 2, 7 } 
    };
 
    int arr[SIZE * SIZE];
    arr2DTo1D(arr2d, SIZE, SIZE, arr);
 
    for (int i = 0; i < SIZE * SIZE; i++) {
        printf("%d ", arr[i]);
    }
 
    return 0;
}
 
 
  
/*
run:
  
5 6 1 3 8 0 9 2 7 
  
*/

 

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Answer 2

#include <stdio.h>

#define ROWS 3
#define COLS 4
#define SIZE ROWS * COLS

void arr2DTo1D(int arr2d[][COLS], int rows, int cols, int arr[]) {
    int k = 0;
    
    for (int i = 0; i < rows; i++) {
        for (int j = 0; j < cols; j++) {
            arr[k++] = arr2d[i][j];
        }
    }
}

int main() {
    int arr2d[ROWS][COLS] = { 
        { 5, 6, 1, 4 }, 
        { 3, 8, 0, 2 },
        { 9, 2, 7, 1 } 
    };

    int arr[SIZE];
    arr2DTo1D(arr2d, ROWS, COLS, arr);

    for (int i = 0; i < SIZE; i++) {
        printf("%d ", arr[i]);
    }

    return 0;
}


 
/*
run:
 
5 6 1 4 3 8 0 2 9 2 7 1 
 
*/

 

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