Memory Layout of Arrays

Examining the memory allocation and addressing of one-dimensional and two-dimensional arrays.

#include <stdio.h>

#define DIM1 4
#define DIM2 2

void display_1d_array(int arr[], int len) {
    printf("Array size in bytes: %lu\n", sizeof(arr));
    for (int idx = 0; idx < len; ++idx) {
        printf("[%p]: %d\n", (void*)&arr[idx], arr[idx]);
    }
    printf("Array name address: %p\n", (void*)arr);
}

void display_2d_array(int mat[][DIM1], int rows, int cols) {
    printf("2D array size in bytes: %lu\n", sizeof(mat));
    for (int r = 0; r < rows; ++r) {
        for (int c = 0; c < cols; ++c) {
            printf("[%p]: %d\n", (void*)&mat[r][c], mat[r][c]);
        }
    }
    printf("Array name: %p\n", (void*)mat);
    printf("First row: %p\n", (void*)mat[0]);
    printf("Second row: %p\n", (void*)mat[1]);
}

int main() {
    int single_dim[DIM1] = {10, 20, 30, 40};
    int double_dim[DIM2][DIM1] = {{1, 2, 3, 4}, {5, 6, 7, 8}};

    display_1d_array(single_dim, DIM1);
    display_2d_array(double_dim, DIM2, DIM1);

    return 0;
}

Note: The sizeof operator on an array paarmeter in a function returns the size of a pointer, not the array.

Function with Array Parameters

Passing arrays to functions for processing.

Compute Trimmed Mean

Calcluate the average of an array after removing the maximum and minimum values.

#include <stdio.h>
#define MAX_SIZE 100

void read_values(int arr[], int count) {
    for (int i = 0; i < count; ++i) {
        scanf("%d", &arr[i]);
    }
}

double calculate_trimmed_average(int data[], int size) {
    if (size <= 2) return 0.0;
    int max_val = data[0];
    int min_val = data[0];
    double total = 0.0;

    for (int i = 0; i < size; ++i) {
        total += data[i];
        if (data[i] > max_val) max_val = data[i];
        if (data[i] < min_val) min_val = data[i];
    }
    return (total - max_val - min_val) / (size - 2);
}

int main() {
    int dataset[MAX_SIZE];
    int num_elements;
    while (scanf("%d", &num_elements) != EOF) {
        read_values(dataset, num_elements);
        double result = calculate_trimmed_average(dataset, num_elements);
        printf("Result: %.2f\n", result);
    }
    return 0;
}

Matrix Initialization and Printing

Fill a square matrix with a given value and print its contents.

#include <stdio.h>
#define MAX_DIM 100

void fill_matrix(int mat[][MAX_DIM], int dim, int val) {
    for (int r = 0; r < dim; ++r) {
        for (int c = 0; c < dim; ++c) {
            mat[r][c] = val;
        }
    }
}

void print_matrix(int mat[][MAX_DIM], int dim) {
    for (int r = 0; r < dim; ++r) {
        for (int c = 0; c < dim; ++c) {
            printf("%d ", mat[r][c]);
        }
        printf("\n");
    }
}

Median Calculation

Sort an array and find its median value.

#include <stdio.h>
#define MAX_LEN 100

void get_input(int arr[], int len) {
    for (int i = 0; i < len; ++i) {
        scanf("%d", &arr[i]);
    }
}

double find_median(int arr[], int len) {
    for (int i = 0; i < len - 1; ++i) {
        for (int j = 0; j < len - i - 1; ++j) {
            if (arr[j] > arr[j+1]) {
                int temp = arr[j];
                arr[j] = arr[j+1];
                arr[j+1] = temp;
            }
        }
    }
    if (len % 2 == 1) {
        return (double)arr[len/2];
    } else {
        return ((double)arr[len/2 - 1] + (double)arr[len/2]) / 2.0;
    }
}

Matrix Operations

Column Cyclic Shift

Shift all columns of a square matrix to the right by one position, with the last column wrapping around to the first.

#include <stdio.h>
#define MAX_SZ 100

void populate_matrix(int mat[][MAX_SZ], int sz) {
    for (int i = 0; i < sz; ++i) {
        for (int j = 0; j < sz; ++j) {
            scanf("%d", &mat[i][j]);
        }
    }
}

void display_matrix(int mat[][MAX_SZ], int sz) {
    for (int i = 0; i < sz; ++i) {
        for (int j = 0; j < sz; ++j) {
            printf("%4d", mat[i][j]);
        }
        printf("\n");
    }
}

void shift_columns_right(int mat[][MAX_SZ], int sz) {
    int temp_col[MAX_SZ];
    for (int i = 0; i < sz; ++i) {
        temp_col[i] = mat[i][sz-1];
    }
    for (int j = sz-1; j > 0; --j) {
        for (int i = 0; i < sz; ++i) {
            mat[i][j] = mat[i][j-1];
        }
    }
    for (int i = 0; i < sz; ++i) {
        mat[i][0] = temp_col[i];
    }
}

Number Base Conversion

Convert a decimal integer to binary, octal, or hexadecimal representation.

#include <stdio.h>
#define BUF_SIZE 100

void convert_base(int decimal, int base) {
    if (decimal == 0) {
        printf("0");
        return;
    }
    char buffer[BUF_SIZE];
    int idx = 0;
    int num = decimal;
    while (num > 0) {
        int remainder = num % base;
        if (base == 16 && remainder >= 10) {
            buffer[idx++] = 'A' + remainder - 10;
        } else {
            buffer[idx++] = '0' + remainder;
        }
        num /= base;
    }
    for (int j = idx - 1; j >= 0; --j) {
        printf("%c", buffer[j]);
    }
}