C Macro-Based Quick Sort for 3-Vectors

Here's a quick macro sort implementation in C for a three-vector:

#include <stdio.h>

#define SWAP(x, y) do { typeof(x) temp = x; x = y; y = temp; } while (0)

void quickSort(int arr[][3], int left, int right) {
    int i, j, pivot;

    if (left < right) {
        pivot = left;
        i = left;
        j = right;

        while (i < j) {
            while (arr[i][0] <= arr[pivot][0] && i < right)
                i++;
            while (arr[j][0] > arr[pivot][0])
                j--;
            if (i < j) {
                SWAP(arr[i][0], arr[j][0]);
                SWAP(arr[i][1], arr[j][1]);
                SWAP(arr[i][2], arr[j][2]);
            }
        }

        SWAP(arr[pivot][0], arr[j][0]);
        SWAP(arr[pivot][1], arr[j][1]);
        SWAP(arr[pivot][2], arr[j][2]);

        quickSort(arr, left, j - 1);
        quickSort(arr, j + 1, right);
    }
}

int main() {
    int arr[][3] = {{3, 2, 1}, {1, 3, 2}, {2, 1, 3}, {1, 2, 3}, {3, 1, 2}};
    int n = sizeof(arr) / sizeof(arr[0]);
    int i;

    printf("Before sorting:\n");
    for (i = 0; i < n; i++) {
        printf("%d %d %d\n", arr[i][0], arr[i][1], arr[i][2]);
    }

    quickSort(arr, 0, n - 1);

    printf("\nAfter sorting:\n");
    for (i = 0; i < n; i++) {
        printf("%d %d %d\n", arr[i][0], arr[i][1], arr[i][2]);
    }

    return 0;
}

Explanation:

• The quickSort function takes an array arr, left index left, and right index right as parameters.
• It selects a pivot element from the array (in this case, the element at index left), and partitions the array such that all elements smaller than the pivot are on its left, and all elements greater than the pivot are on its right.
• It then recursively applies the same process to the left and right partitions until the array is sorted.
• The SWAP macro is used to swap elements in the array.
• In the main function, a sample array arr is defined and its size n is calculated.
• The array is printed before sorting.
• The quickSort function is called with the array, left index 0, and right index n-1.
• Finally, the sorted array is printed.