Different sorting algorithms implementation

sort.c

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

void isort(int a[], int len) {
	int key, i,j;
	for(i=1; i < len; ++i) {
		key = a[i];
		for(j=i-1; j>=0 && key < a[j]; --j) {
			a[j+1] = a[j];
		}
		a[j+1] = key;
	}
}

void ssort(int a[], int len) {
	int min, min_id, temp, i, j;

	for(i=0; i<len-1;++i) {
		min_id = i;
		for(j=i+1;j<len;++j) {
			if(a[j] < a[min_id]) {
				min_id = j;
			}
		}
		temp = a[i];
		a[i] = a[min_id];
		a[min_id] = temp;

	}
}
void msort(int a[], int p, int q, int r) {
	int t[10];
	int i,j,k,m; 
	j=p;
	m=q+1;
	for(i=p; j<=q && m<=r ; i++)
	{
		if(a[j]<=a[m])
		{
			t[i]=a[j];
			j++;
		}
		else
		{
			t[i]=a[m];
			m++;
		}
	}
	if(j>q)
	{
		for(k=m; k<=r; k++)
		{
			t[i]=a[k];
			i++;
		}
	}
	else
	{
		for(k=j; k<=q; k++)
		{
			t[i]=a[k];
			i++;
		}
	}
	for(k=p; k<=r; k++) {
		a[k]=t[k];
	}
	

}

void qusort(int a[], int too_big_index, int too_small_index) {
	int pivot,j,temp,i;

	if(too_big_index<too_small_index){
		pivot=too_big_index;
		i=too_big_index;
		j=too_small_index;

		while(i<j){
			while(a[i]<=a[pivot]&&i<too_small_index)
				i++;
			while(a[j]>a[pivot])
				j--;
			if(i<j){
				temp=a[i];
				a[i]=a[j];
				a[j]=temp;
			}
		}

		temp=a[pivot];
		a[pivot]=a[j];
		a[j]=temp;
		qusort(a,too_big_index,j-1);
		qusort(a,j+1,too_small_index);

	}
}


void merge(int a[], int l, int r) {
	int centre;
	if(l<r) {
		centre = (l + r)/2;
		merge(a, l, centre);
		merge(a, centre+1, r);
		msort(a, l, centre, r);
	}
}




int main() {
	int a[10], i;
	int choice;
	printf("Enter 10 values: ");
	for(i=0; i<10;++i) {
		scanf("%d", &a[i]);
	}
	while(1) {
		printf("1. Insertion sort\n"
			"2. Selection sort\n"
			"3. Merge sort\n"
			"4. Quick sort\n"
			"5. Print array\n");
		printf("Enter an option:");
		scanf("%d", &choice);

		switch(choice) {
			case 1:
				isort(a, 10);
				break;
			case 2:
				ssort(a, 10);
				break;
			case 3:
				merge(a, 0, 9);
				break;
			case 4:
				qusort(a, 0, 9);
				break;
			case 5:
				for(i=0; i<10;++i) {
					printf("%d ", a[i]);
				}
				printf("\n");
				break;
			default:
				exit(0);
		}
	}


}