Two-Dimensional Arrays in C (2D Arrays)

Declaration of 2D Array

data_type array_name[rows][cols];

int matrix[3][3];

Initialization of 2D Array

int a[2][3] = {
    {1, 2, 3},
    {4, 5, 6}
};

int a[2][3] = {1, 2, 3, 4, 5, 6};

Practical Example 1 – Print Matrix

#include <stdio.h>

int main() {

    int a[2][3] = { {1,2,3}, {4,5,6} };

    for(int i = 0; i < 2; i++){
        for(int j = 0; j < 3; j++){
            printf("%d ", a[i][j]);
        }
        printf("\n");
    }

    return 0;
}

Practical Example 2 – Sum of All Elements

#include <stdio.h>

int main() {

    int m[3][3] = {
        {2, 4, 6},
        {1, 3, 5},
        {7, 9, 8}
    };

    int sum = 0;

    for(int i = 0; i < 3; i++){
        for(int j = 0; j < 3; j++){
            sum += m[i][j];
        }
    }

    printf("Total Sum = %d", sum);

    return 0;
}

Practical Example 3 – Sum of Each Row

#include <stdio.h>

int main() {

    int a[3][3] = {
        {5,1,3},
        {2,7,4},
        {6,9,8}
    };

    for(int i = 0; i < 3; i++){
        int sum = 0;
        for(int j = 0; j < 3; j++){
            sum += a[i][j];
        }
        printf("Row %d sum = %d\n", i+1, sum);
    }

    return 0;
}

Practical Example 4 – Sum of Each Column

#include <stdio.h>

int main() {

    int a[3][3] = {
        {3,5,7},
        {1,4,6},
        {8,2,9}
    };

    for(int col = 0; col < 3; col++){
        int sum = 0;

        for(int row = 0; row < 3; row++){
            sum += a[row][col];
        }

        printf("Column %d sum = %d\n", col+1, sum);
    }

    return 0;
}

Practical Example 5 – Print Diagonal Elements

#include <stdio.h>

int main() {

    int m[3][3] = {
        {1,2,3},
        {4,5,6},
        {7,8,9}
    };

    printf("Main diagonal: ");
    for(int i = 0; i < 3; i++){
        printf("%d ", m[i][i]);
    }

    printf("\nSecondary diagonal: ");
    for(int i = 0; i < 3; i++){
        printf("%d ", m[i][2-i]);
    }

    return 0;
}

Practical Example 6 – Transpose of Matrix

#include <stdio.h>

int main() {

    int m[2][3] = {
        {1,2,3},
        {4,5,6}
    };

    printf("Transpose:\n");

    for(int col = 0; col < 3; col++){
        for(int row = 0; row < 2; row++){
            printf("%d ", m[row][col]);
        }
        printf("\n");
    }

    return 0;
}

Practical Example 7 – Matrix Addition

#include <stdio.h>

int main() {

    int a[2][2] = { {1,2}, {3,4} };
    int b[2][2] = { {5,6}, {7,8} };
    int sum[2][2];

    for(int i = 0; i < 2; i++){
        for(int j = 0; j < 2; j++){
            sum[i][j] = a[i][j] + b[i][j];
        }
    }

    printf("Sum matrix:\n");

    for(int i = 0; i < 2; i++){
        for(int j = 0; j < 2; j++){
            printf("%d ", sum[i][j]);
        }
        printf("\n");
    }

    return 0;
}

Practical Example 8 – Matrix Multiplication (2x2)

#include <stdio.h>

int main() {

    int a[2][2] = { {1,2}, {3,4} };
    int b[2][2] = { {2,0}, {1,2} };
    int res[2][2];

    for(int i = 0; i < 2; i++){
        for(int j = 0; j < 2; j++){
            res[i][j] = 0;
            for(int k = 0; k < 2; k++){
                res[i][j] += a[i][k] * b[k][j];
            }
        }
    }

    printf("Result matrix:\n");

    for(int i = 0; i < 2; i++){
        for(int j = 0; j < 2; j++){
            printf("%d ", res[i][j]);
        }
        printf("\n");
    }

    return 0;
}

Practical Example 9 – Count Even Numbers in Matrix

#include <stdio.h>

int main() {

    int m[3][3] = {
        {2,3,4},
        {5,6,7},
        {8,9,10}
    };

    int count = 0;

    for(int i = 0; i < 3; i++){
        for(int j = 0; j < 3; j++){
            if(m[i][j] % 2 == 0)
                count++;
        }
    }

    printf("Even count = %d", count);

    return 0;
}

Practical Example 10 – Search Element in 2D Array

#include <stdio.h>

int main() {

    int m[3][3] = {
        {4,7,1},
        {3,9,2},
        {8,6,5}
    };

    int key = 9, found = 0;

    for(int i = 0; i < 3; i++){
        for(int j = 0; j < 3; j++){
            if(m[i][j] == key){
                found = 1;
                break;
            }
        }
    }

    if(found)
        printf("Found");
    else
        printf("Not Found");

    return 0;
}

Practice Questions

1. Create a 3×3 matrix and print it.
2. Find the largest element in a 2D array.
3. Calculate row-wise and column-wise sums.
4. Transpose a 4×4 matrix.
5. Search an element in a matrix.

Practice Task