A quicksort implementation collection in C

quicksort.c

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

void qsort_last(int s[], int start_index, int end_index);	//select the last element as the pivot
void qsort_first(int s[], int start_index, int end_index);	//select the first element as the pivot
void qsort_mid(int s[], int start_index, int end_index);	//select the middle element as the pivot
void qsort_rand(int s[], int start_index, int end_index);	//select a random index's value as the pivot
void qsort_mot(int s[], int start_index, int end_index);	//median of three partitioning + insertion sort
void qsort_clrs(int s[], int start_index, int end_index);	//select the last element as the pivot, CLRS version
int partition(int s[], int start_index, int end_index);
int getPivot(int s[], int start_index, int end_index);	
int medianOfThree(int s[], int start_index, int end_index);
void insertionSort(int s[], int start_index, int end_index);
void bubbleSort(int s[], int start_index, int end_index);

int main()
{
	int i;
	int s[100];
	srand(time(0));
	for(i = 0; i < 100; ++i){
		s[i] = rand() % 100;
	}
	// int s[] = {1, 8, 5, 6, 9, 7, 1, 2, 3, 2, 0, 19};
	// int s[] = {1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1};
	// int s[] = {12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1};
	// int s[] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12};
	// qsort_mot(s, 0, 99);
	// qsort_first(s, 0, 99);
	// qsort_last(s, 0, 99);
	// qsort_mid(s, 0, 99);
	// qsort_rand(s, 0, 99);
	qsort_mot(s, 0, 99);
	// insertionSort(s, 0, 99);
	// bubbleSort(s, 0, 99);
	for(i = 0; i < 100; ++i){
		printf("%d ", s[i]);
		if(i % 10 == 9){
			printf("\n");
		}
	}

	return 0;
}

void qsort_last(int s[], int start_index, int end_index){
	if(start_index < end_index){
		//the number of elements in s larger than 2

		//get the pivot
		int pivot = s[end_index];	//select the last element as the pivot(needn't to consider i out of range)

		//split s into two pieces
		int i = start_index, j = end_index - 1;
		int temp;
		while(i <= j){
			while(s[i] < pivot){ i++; }
			// printf("i = %d\n", i); 
			while(s[j] > pivot && i < j){ j--; }
			// printf("j = %d\n", j);
			// printf("\n");
			//swap the elements where i, j stop
			if(i < j){
				temp = s[j];
				s[j] = s[i];
				s[i] = temp;
				i++;
				j--;
			}else {
				break;
			}
		}
		//swap the pivot to middle
		s[end_index] = s[i];
		s[i] = pivot;
		
		//recursion
		qsort_last(s, start_index, i - 1);
		qsort_last(s, i + 1, end_index);
	}
}

void qsort_first(int s[], int start_index, int end_index){
	if(start_index < end_index){
		int pivot = s[start_index];	//no need to consider j out of range
		int i = start_index + 1, j = end_index;
		int temp;
		while(i <= j){
			while(s[i] < pivot && i < j){ i++; }
			// printf("i = %d ", i); 
			while(s[j] > pivot){ j--; }
			// printf("j = %d ", j); 
			// printf("\n");
			if(i < j){
				temp = s[j];
				s[j] = s[i];
				s[i] = temp;
				i++;
				j--;
			}else {
				break;
			}
		}
		s[start_index] = s[j];
		s[j] = pivot;

		//recursion
		qsort_first(s, start_index, j - 1);
		qsort_first(s, j + 1, end_index);
	}
}

void qsort_mid(int s[], int start_index, int end_index){
	if(start_index < end_index){
		int pivot = s[(start_index + end_index) / 2];	//select the middle element as the pivot
		int i = start_index, j = end_index;
		int temp;
		while(i <= j){
			while(s[i] < pivot && i <= j){ i++; }	//no need to consider i & j out of range
			while(s[j] > pivot && i <= j){ j--; }
			if(i <= j){
				temp = s[j];
				s[j] = s[i];
				s[i] = temp;
				i++;
				j--;
			}else {
				break;
			}
		}
		// printf("i = %d j = %d\n", i, j);
		qsort_mid(s, start_index, j);
		qsort_mid(s, i, end_index);
	}
}

int getPivot(int s[], int start_index, int end_index){
	srand(time(0));
	int index = (rand() % (end_index - start_index + 1)) + start_index;
	// printf("index = %d ", index);
	return s[index];
}

void qsort_rand(int s[], int start_index, int end_index){
	if(start_index < end_index){
		int pivot = getPivot(s, start_index, end_index);
		// printf("pivot = %d\n", pivot);
		int i = start_index, j = end_index;
		int temp;
		while(i <= j){
			while(s[i] < pivot && i <= j){ i++; }
			while(s[j] > pivot && i <= j){ j--; }
			if(i <= j){
				temp = s[j];
				s[j] = s[i];
				s[i] = temp;
				i++;
				j--;
			}else {
				break;
			}
		}
		qsort_rand(s, start_index, j);
		qsort_rand(s, i, end_index);
	}
}

int medianOfThree(int s[], int start_index, int end_index){
	int temp;
	if(s[start_index] > s[(start_index + end_index) / 2]){
		temp = s[(start_index + end_index) / 2];
		s[(start_index + end_index) / 2] = s[start_index];
		s[start_index] = temp;
	}
	if(s[(start_index + end_index) / 2] > s[end_index]){
		temp = s[(start_index + end_index) / 2];
		s[(start_index + end_index) / 2] = s[end_index];
		s[end_index] = temp;
	}
	if(s[start_index] > s[(start_index + end_index) / 2]){
		temp = s[(start_index + end_index) / 2];
		s[(start_index + end_index) / 2] = s[start_index];
		s[start_index] = temp;
	}
	//swap the pivot to end_index - 1 positon
	// temp = s[end_index - 1];
	// s[end_index - 1] = s[(start_index + end_index) / 2];
	// s[(start_index + end_index) / 2] = temp;
	// return s[end_index - 1];
	return s[(start_index + end_index) / 2];
}

void qsort_mot(int s[], int start_index, int end_index){
	int cutoff = 3;
	int pivot = medianOfThree(s, start_index, end_index);
	//printf("pivot = %d\n", pivot);
	if(start_index + cutoff <= end_index){
		int i = start_index + 1, j = end_index - 1;
		int temp;
		while(i <= j){
			while(s[i] < pivot && i <= j){ i++; }
			while(s[j] > pivot && i <= j){ j--; }
			if(i <= j){
				temp = s[j];
				s[j] = s[i];
				s[i] = temp;
				i++;
				j--;
			}else {
				break;
			}
		}
		//swap pivot back
		// s[end_index - 1] = s[i];
		// s[i] = pivot;
		qsort_mot(s, start_index, j);
		qsort_mot(s, i, end_index);
	}else {
		//insertionSort(s, start_index, end_index);
		insertionSort(s, start_index, end_index);
	}
	
}

void insertionSort(int s[], int start_index, int end_index){
	if(start_index < end_index){
		int i = start_index + 1, j;
		int temp;
		while(i <= end_index){
			temp = s[i];
			j = i - 1;
			while(j >= start_index && s[j] > temp){
				s[j + 1] = s[j];
				j--;
			}
			s[j + 1] = temp;
			i++;
		}
	}
}

void bubbleSort(int s[], int start_index, int end_index){
	int i, j;
	int temp;
	for(i = start_index; i < end_index; i++){
		for(j = start_index; j < end_index - i; j++){
			if(s[j] > s[j + 1]){
				temp = s[j + 1];
				s[j + 1] = s[j];
				s[j] = temp;
			}
		}
	}
}

void qsort_clrs(int s[], int start_index, int end_index){
	if(start_index < end_index){
		//partition
		int pivot_index = partition(s, start_index, end_index);
		// printf("pivot_index = %d\n", pivot_index);

		//recursion
		qsort_clrs(s, start_index, pivot_index - 1);
		qsort_clrs(s, pivot_index + 1, end_index);
	} else if(start_index == end_index) {
	    // only one element
	    return;
	} else {
	    printf("IndexError.");
	    return;
	}
}

int partition(int s[], int start_index, int end_index){
	int i, j = start_index, temp;
	int pivot = s[end_index];	//select the last element as pivot
	for(i = start_index; i < end_index; i++){
		//j表示最靠左的>=pivot的位置
		//发现s[i] < pivot, 则把s[i]和最靠左的>=pivot交换，以保证start_index到i - 1是分割好的。
		if(s[i] < pivot){
			//swap s[i] and s[j]
			temp = s[j];
			s[j] = s[i];
			s[i] = temp;

			j++;
		}
	}
	//swap the pivot to middle (j)
	s[end_index] = s[j];
	s[j] = pivot;

	return j;
}