quickSort-C

#include<stdio.h>
#include<stdlib.h>
#include<time.h>

void swap(int *a, int *b)
{
    int temp = *a;
    *a = *b;
    *b = temp;
}

int partition(int a[], int low, int high)
{
    int pivot = a[low];
    int i = low + 1;
    int j = high;

    while(1)
    {
        while(i <= high && a[i] <= pivot)
            i++;

        while(a[j] > pivot)
            j--;

        if(i < j)
            swap(&a[i], &a[j]);
        else
            break;
    }

    swap(&a[low], &a[j]);
    return j;
}

void quickSort(int a[], int low, int high)
{
    if(low < high)
    {
        int p = partition(a, low, high);
        quickSort(a, low, p - 1);
        quickSort(a, p + 1, high);
    }
}

// generate random numbers
void generateRandomNumbers(int a[], int n)
{
    for(int i = 0; i < n; i++)
        a[i] = rand() % 10000;
}

int main()
{
    int a[10000];
    clock_t start, end;
    double time_taken;
    double theoretical_time;
    FILE *fp;

    srand((unsigned)time(NULL));

    fp = fopen("q_time.txt", "w");

    if(fp == NULL)
    {
        printf("File cannot be opened\n");
        return 1;
    }

    for(int n = 100; n < 10000; n += 100)
    {
        generateRandomNumbers(a, n);

        start = clock();
        quickSort(a, 0, n - 1);
        end = clock();

        time_taken = (double)(end - start) / CLOCKS_PER_SEC;

        // theoretical n log n
        theoretical_time = (double)(n * log(n)) * 1e-7;

        fprintf(fp, "%d %lf %lf\n", n, time_taken, theoretical_time);
    }

    fclose(fp);

    FILE *gP = popen("gnuplot -persistent", "w");

    if(gP == NULL)
    {
        printf("Gnuplot not found\n");
        return 1;
    }

    fprintf(gP, "set title 'Quick Sort Time Efficiency'\n");
    fprintf(gP, "set xlabel 'Input Size'\n");
    fprintf(gP, "set ylabel 'Time (seconds)'\n");
    fprintf(gP, "set grid\n");
    fprintf(gP, "set term png\n");
    fprintf(gP, "set output 'Q_sort_efficiency_c.png'\n");

    fprintf(gP, "plot 'q_time.txt' using 1:2 with linespoints title 'Actual Time',");
    fprintf(gP, "'q_time.txt' using 1:3 with lines lw 2 title 'Theoretical Time'\n");

    fflush(gP);
    pclose(gP);

    return 0;
}