Cracking The Coding Interview 9.0

#include <iostream>
#include <vector>
using namespace std;

void mswap(int &a, int &b)
{
	int c = a;
	a = b;
	b = c;
}

void print(int *a, int size)
{
	for (int i = 0; i<size ; i++)
	{
		cout<<a[i]<<"   ";
	}
}
//Start at the beginning of an array and swap the first two elements if the first is bigger than
//	the second Go to the next pair, etc, continuously making sweeps of the array until sorted
//	O(n^2)
void bubbleSort(int *a, int size)
{
	if (a == NULL || size<0)
	{
		return;
	}
	for (int j = 0; j <size ; j ++)
	{
		for (int i = 0; i< size-1-j; i++)
		{
			if (a[i] > a[i+1])
			{
				mswap(a[i], a[i+1]);
			}
		}
}

}

//Find the smallest element using a linear scan and move it to the front Then, find the second
//	smallest and move it, again doing a linear scan Continue doing this until all the elements
//	are in place O(n^2)
void selectSort(int *a, int size)
{
	if (a == NULL || size<0)
	{
		return;
	}
	for (int i = 0; i<size ;i ++)
	{
		int k = i;
		for (int j = i; j<size; j++)
		{
			if (a[k] > a[j])
			{
				k = j;
			}
		}
		swap(a[k],a[i]);
	}
}

//Sort each pair of elements Then, sort every four elements by merging every two pairs Then,
//sort every 8 elements, etc O(n log n) expected and worst case

void mSort(int *a, int begin, int end, int* temp)
{
	if (a == NULL)
	{
		return;
	}
	int mid = (begin + end)/2;
	int i = begin;
	int j = mid+1;
	int p = 0;

	while (i<=mid && j<=end)
	{
		if (a[i]>a[j])
		{
			temp[p] = a[j];
			p++;
			j++;
		}

		else
		{
			temp[p] = a[i];
			p++;
			i++;
		}

	}

	while(i<=mid)
	{
		temp[p] = a[i];
		p++;
		i++;
	}

	while(j<=end)
	{
		temp[p] = a[j];
		p++;
		j++;
	}
	for (i = 0; i < p; i++)
		a[begin + i] = temp[i];
}

void merge(int *a, int begin, int end, int *temp)
{
	if (begin<end)
	{
		int mid = (begin + end)/2;
		merge(a,begin,mid,temp);
		merge(a,mid +1,end,temp);
		mSort(a,begin,end,temp);
	}
}
//Quick Sort
//Pick a random element and partition the array, such that all numbers that are less than it
//	come before all elements that are greater than it Then do that for each half, then each
//quarter	etc O(n log n) expected, O(n^2) worst case.

int partion(int *a, int begin, int end)
{
	int t = a[begin];
	int low = begin;
	int high = end;
	while(low < high)
	{
		while(low < high&& t<=a[high])
		{
			high--;
		}
		mswap(a[low],a[high]);

		while(low < high && t>=a[low])
		{
			low++;
		}
		mswap(a[low],a[high]);

	}
	return low;
}

void quickSort(int *a, int begin, int end)
{
	if (begin < end)
	{
		int i = partion(a, begin, end);
		quickSort(a, begin, i-1);
		quickSort(a, i + 1, end);
	}
}

int main()
{
	int a[] = {78, 17, 39, 26, 72, 94, 21, 12, 23, 91};
	//bubbleSort(a,6);
	//selectSort(a,6);
//	int *p = new int[6];
//	merge(a,0,5,p);
//	quickSort(a,0,5);

	print(a,10);

	return 0;
}