1+ #include " bits/stdc++.h"
2+ using namespace std ;
3+ void printArr (int arr[], int n,string s=" \n "
4+ if (s==" "
5+ for (int i=0 ;i<n;i++){
6+ cout<<arr[i]<<" "
7+ }
8+ cout<<endl;
9+ }
10+ else {
11+ for (int i=0 ;i<n;i++){
12+ cout<<arr[i]<<' \n '
13+ }
14+ }
15+ }
16+ int merge (int left[], int right[], int arr[], int leftLength, int rightLength){
17+ int i=0 ,j=0 ,k = 0 ;
18+ int inversions = 0 ;
19+ while (i< leftLength && j<rightLength){
20+ if (left[i]<=right[j]){
21+ arr[k]= left[i];
22+ i++;
23+ k++;
24+ }
25+ else {
26+ arr[k] = right[j];
27+ j++;
28+ k++;
29+ inversions += leftLength - i;
30+ }
31+ }
32+ while (i<leftLength){
33+ arr[k] = left[i];
34+ i++;
35+ k++;
36+ // inversions += rightLength;
37+ 38+ }
39+ while (j<rightLength){
40+ arr[k] = right[j];
41+ j++;
42+ k++;
43+ }
44+ return inversions;
45+ }
46+ int mergeSort (int arr[], int n){
47+ int mid = n/2 ;
48+ if (n<2 ){
49+ return 0 ;
50+ }
51+ int left[mid];
52+ int right[n-mid];
53+ 54+ for (int i = 0 ; i<mid;i++){
55+ left[i] = arr[i];
56+ }
57+ // printArr(left, mid," ");
58+ int i = 0 ;
59+ for (int j = mid;j<n;j++){
60+ right[i] = arr[j];
61+ i++;
62+ }
63+ // printArr(right, n-mid," ");
64+ int x = mergeSort (left, mid);
65+ int y = mergeSort (right, n- mid);
66+ int z = merge (left, right, arr,mid, n- mid);
67+ 68+ return x+y+z;
69+ 70+ }
71+ int inversions (int arr[], int n){
72+ int d = 0 ;
73+ for (int i = 0 ;i< n;i++){
74+ for (int j = i+1 ;j<n;j++){
75+ if (arr[i]>arr[j]){
76+ d++;
77+ }
78+ }
79+ }
80+ 81+ return d;}
82+ int main (){
83+ int arr[8 ] = {2 ,1 ,4 ,6 ,7 ,5 ,3 ,8 };
84+ cout<< " Inversions are:" inversions (arr,8 )<<endl;
85+ cout<< " Inversions output:" mergeSort (arr,8 )<<endl;
86+ return 0 ;
87+ }
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