Week 13 - Sorting

Counting Sort
public static void sort (int[] list) {
	int[] sorted = new int[list.length];

	for (int i = 0; i < list.length; i++) {
		int smallerCount = countSmaller (list[i], list);
		sorted[smallerCount] = list[i];
	}
	for (int i = 0; i < list.length; i++) {
		list[i] = sorted[i];
	}
}

// This version doesn't use the countSmaller method.
public static void sort (int[] list) {			(a)
	int[] sorted = new int[list.length];		(a)

	for (int i = 0; i < list.length; i++) {
		int smallerCount = 0;
		for (int j = 0; j < list.length; j++) {
			if (list[j] < list[i]) {		//comp	(b)
				smallerCount++;
			}
		}
		sorted[smallerCount] = list[i];		//move
	}
	for (int i = 0; i < list.length; i++) {
		list[i] = sorted[i];				//move
	}
}



Insertion Sort

// sort: insertion sort works by inserting each value
//       into a previously sorted subset of the list.

public static void sort (int[] list) {
	
	for (int i=1; i < list.length; i++) {
		int key = list[i];
		int pos = i;
		
		// shift larger values to the right
		while(pos>0 && list[pos-1] > key) {
		   list[pos] = list [pos-1];
			pos--;
		}
		list[pos] = key;
	}
}



Selection Sort


// sort: selection sort works by putting each value
//       into its final position, one at a time.

public static void sort (int[] list) {

	for (int i=0; i < list.length - 1; i++) {

		int min = i;  // position of smallest element
		for (int scan=i+1; scan < list.length; scan++) {
		  if (list[scan] < list[min])
				min = scan;
		}

		// Swap
		int temp = list[min];
		list[min] = list[i];
		list[i] = temp;
	}
}


Bubble Sort

// sort: same description as before, as far as the
// user is concerned, but the insides are different!
public static void sort (int[] list) {

	final int N = list.length;

	// N - 1 scans
	for (int scan = 0; scan < N - 1; scan++) {

		// Loop for each pair to be swapped (lower
		// is the index of lower pair to be swapped).
		for (int lower=0; lower<N-1-scan; lower++) {

		  // If out of order, swap the pair.
		  if (list[lower] > list[lower+1]) {
				int temp = list[lower];
				list[lower] = list[lower + 1];
				list[lower + 1] = temp;
		  }
		}
	}
}