mergesort code in python and cpp added

Author: shvbsle

a.out

@@ -43,3 +43,25 @@ table. Coz all keys of the map are initialized to 0. Hence, if a fucntions retur
 
 ============================================================================
 
+Ouuu... While doing merge sort I found a lot of usefull things
+
+vectors; merging vectors in c ++
+
+assume you have 
+std::vector<int> AB, A = {1,2,3,4},B = {5,6,7,8};
+
+then do:
+
+AB.reserve(A.size()+B.size());
+AB.insert(AB.end(), A.begin().A.end());
+AB.insert(AB.end(), B.begin(), B.end());
+
+this will give us AB = {1,2,3,4,5,6,7,8}
+
+-----
+
+Now, to check if a vector is empty: vector.empty() (boolean value return)
+
+to erase an element (or range of elements) in the vector: vector.erase(vector.begin() + index, (optional) vector.begin()+end)
+
+=============================================================================	

cpp_notes.txt

@@ -1,2 +1 @@
-AGGTAB
-GXTXAYB
+12 11 13 5 6 7

ip.txt

@@ -0,0 +1,55 @@
+/*
+A standard divide and conquer algorithm for mergesort
+
+input format
+============
+12 11 13 5 6 7
+==============
+*/
+#include <bits/stdc++.h>
+std::vector<int> v, answer;
+
+std::vector<int> merge(std::vector<int> low, std::vector<int> high){
+	std::vector<int> l, ret;
+	while(!low.empty() && !high.empty()){
+		if(low[0] < high[0]){
+			l.push_back(low[0]);
+			low.erase(low.begin());
+		}
+		else{
+			l.push_back(high[0]);
+			high.erase(high.begin());
+		}
+	}
+	ret.reserve(l.size() + low.size() + high.size());
+	ret.insert(ret.end(), l.begin(), l.end());
+	ret.insert(ret.end(), low.begin(), low.end());
+	ret.insert(ret.end(), high.begin(), high.end());
+	return ret;
+}
+
+std::vector<int> mergesort(int l, int h){
+	std::vector<int> low;
+	std::vector<int> high;
+	int mid = (l+h)/2;
+	if (l < h){
+		low = mergesort(l, mid);
+		high = mergesort(mid+1, h);
+		return merge(low, high);
+	}
+	return {v[l]};
+}
+
+int main(){
+	int temp;
+	for(int i = 0; i<6; i++){
+		std::cin >> temp;
+		v.push_back(temp);
+	}
+
+	answer = mergesort(0, 5);
+	for(int i = 0; i < 6; i++){
+		std::cout << answer[i] << " "; 
+	}
+	return 0;
+}

merge_sort.cpp

@@ -0,0 +1,31 @@
+'''
+A standard divide and conquer algorithm for mergesort
+
+input format
+============
+12 11 13 5 6 7
+==============
+'''
+
+arr = list(map(int, input().split(" ")))
+
+def merge(a,b):
+	l = []
+	while a and b:
+		if a[0] < b[0]:
+			l.append(a.pop(0))
+		else:
+			l.append(b.pop(0))
+	return l + a + b
+
+
+def merge_sort(l, h):
+	mid = int((h+l)/2)
+	if l < h:
+		# print(arr[l: h])
+		low = merge_sort(l, mid)
+		high = merge_sort(mid+1, h)
+		return merge(low, high)
+	# print(arr, l)
+	return [arr[l]]
+print(merge_sort(0, len(arr)-1))