diff --git a/projects/Merge_Sort_Algorithm/README.md b/projects/Merge_Sort_Algorithm/README.md new file mode 100644 index 000000000..be3b0dd8b --- /dev/null +++ b/projects/Merge_Sort_Algorithm/README.md @@ -0,0 +1,31 @@ +## Merge Sort Algorithm + +This script sorts the given array using merge sort algorithm. You can change the predefined "arr" to sort your array. + +### Prerequisites + +You only need python to run this script. You can visit [here](https://www.python.org/downloads/) to download python. + +### How to run the script + +Running the script is really simple! Just open a terminal in the folder where your script is located and run the following command : + +``` +python3 merge.py +``` + +### Sample use of the script + +``` +python3 merge.py + + Given array is + 100 50 80 20 70 + + Sorted array is + 20 50 70 80 100 + +``` +### Author Name + +Vrunda Jasani diff --git a/projects/Merge_Sort_Algorithm/merge.py b/projects/Merge_Sort_Algorithm/merge.py new file mode 100644 index 000000000..5a3319e7d --- /dev/null +++ b/projects/Merge_Sort_Algorithm/merge.py @@ -0,0 +1,77 @@ +# Python program for implementation of MergeSort + +# Merges two subarrays of arr[]. +# First subarray is arr[l..m] +# Second subarray is arr[m+1..r] + + +def merge(arr, l, m, r): + n1 = m - l + 1 + n2 = r - m + + # create temp arrays + L = [0] * (n1) + R = [0] * (n2) + + # Copy data to temp arrays L[] and R[] + for i in range(0, n1): + L[i] = arr[l + i] + + for j in range(0, n2): + R[j] = arr[m + 1 + j] + + # Merge the temp arrays back into arr[l..r] + i = 0 # Initial index of first subarray + j = 0 # Initial index of second subarray + k = l # Initial index of merged subarray + + while i < n1 and j < n2: + if L[i] <= R[j]: + arr[k] = L[i] + i += 1 + else: + arr[k] = R[j] + j += 1 + k += 1 + + # Copy the remaining elements of L[], if there + # are any + while i < n1: + arr[k] = L[i] + i += 1 + k += 1 + + # Copy the remaining elements of R[], if there + # are any + while j < n2: + arr[k] = R[j] + j += 1 + k += 1 + +# l is for left index and r is right index of the +# sub-array of arr to be sorted + +def mergeSort(arr, l, r): + if l < r: + + # Same as (l+r)//2, but avoids overflow for + # large l and h + m = l+(r-l)//2 + + # Sort first and second halves + mergeSort(arr, l, m) + mergeSort(arr, m+1, r) + merge(arr, l, m, r) + + +# Driver code to test above +arr = [100, 50, 80, 25, 20, 5] +n = len(arr) +print("Given array is") +for i in range(n): + print("%d" % arr[i],end=" ") + +mergeSort(arr, 0, n-1) +print("\n\nSorted array is") +for i in range(n): + print("%d" % arr[i],end=" ") \ No newline at end of file