timSort.cpp

// C++ program to perform TimSort.

#include <bits/stdc++.h>

using namespace std;
const int RUN = 32;

// this function sorts array from left index to
// to right index which is of size atmost RUN
void insertionSort(int arr[], int left, int right)
{
	for (int i = left + 1; i <= right; i++)
	{
		int temp = arr[i];
		int j = i - 1;
		while (j >= left && arr[j] > temp)
		{
			arr[j + 1] = arr[j];
			j--;
		}
		arr[j + 1] = temp;
	}
}

// merge function merges the sorted runs
void merge(int arr[], int l, int m, int r)
{
	// original array is broken in two parts
	// left and right array
	int len1 = m - l + 1, len2 = r - m;
	int left[len1], right[len2];
	for (int i = 0; i < len1; i++)
		left[i] = arr[l + i];
	for (int i = 0; i < len2; i++)
		right[i] = arr[m + 1 + i];

	int i = 0;
	int j = 0;
	int k = l;

	// after comparing, we merge those two array
	// in larger sub array
	while (i < len1 && j < len2)
	{
		if (left[i] <= right[j])
		{
			arr[k] = left[i];
			i++;
		}
		else
		{
			arr[k] = right[j];
			j++;
		}
		k++;
	}

	// copy remaining elements of left, if any
	while (i < len1)
	{
		arr[k] = left[i];
		k++;
		i++;
	}

	// copy remaining element of right, if any
	while (j < len2)
	{
		arr[k] = right[j];
		k++;
		j++;
	}
}

// iterative Timsort function to sort the
// array[0...n-1] (similar to merge sort)
void timSort(int arr[], int n)
{
	// Sort individual subarrays of size RUN
	for (int i = 0; i < n; i += RUN)
		insertionSort(arr, i, min((i + 31), (n - 1)));

	// start merging from size RUN (or 32). It will merge
	// to form size 64, then 128, 256 and so on ....
	for (int size = RUN; size < n; size = 2 * size)
	{
		// pick starting point of left sub array. We
		// are going to merge arr[left..left+size-1]
		// and arr[left+size, left+2*size-1]
		// After every merge, we increase left by 2*size
		for (int left = 0; left < n; left += 2 * size)
		{
			// find ending point of left sub array
			// mid+1 is starting point of right sub array
			int mid = left + size - 1;
			int right = min((left + 2 * size - 1), (n - 1));

			// merge sub array arr[left.....mid] &
			// arr[mid+1....right]
			merge(arr, left, mid, right);
		}
	}
}

// utility function to print the Array
void printArray(int arr[], int n)
{
	for (int i = 0; i < n; i++)
		printf("%d ", arr[i]);
	printf("\n");
}

// Driver program to test above function
int main()
{
	int arr[] = {5, 21, 7, 23, 19};
	int n = sizeof(arr) / sizeof(arr[0]);
	printf("Given Array is\n");
	printArray(arr, n);

	timSort(arr, n);

	printf("After Sorting Array is\n");
	printArray(arr, n);
	return 0;
}