C Quick Sort

You can select the s randomly. This way may avoid the worst case.

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#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#define MAX 10
#define SWAP(x,y) {int t; t = x; x = y; y = t;}

int partition(int number[], int left, int right) {
    int i, j, s;
    s = number[right];
    i = left - 1;
    for(j = left; j < right; j++)  {
        if(number[j] <= s)  {
            i++;
            SWAP(number[i], number[j]);
        }
    }
    SWAP(number[i+1], number[right]);
    return i+1;
}

void quicksort(int number[], int left, int right) {
    int q;

    if(left < right) {
        q = partition(number, left, right);
        quicksort(number, left, q-1);
        quicksort(number, q+1, right);
    }
}

int main(void) {
    int number[MAX] = {0};
    int i, num;
    srand(time(NULL));

    printf("Before Sort:");
    for(i = 0; i < MAX; i++)  {
        number[i] = rand() % 100;        
        printf("%d ", number[i]);    
    }
    quicksort(number, 0, MAX-1);    
    printf("\nAfter Sort:");
    for(i = 0; i < MAX; i++)        
        printf("%d ", number[i]); 
    printf("\n");
    printf("Press any key to end...\n");    
    getchar();
    return 0;
}