change implementation to merge-sort

sorting.cpp

-#include<vector>
+#include<iostream>
+#include"sorting.h"
+
 
 using namespace std;
 
+
+vector<int> mergeSorting(vector<int> arr);
+vector<int> mergeSorting(vector<int> v);
+vector<int> merge(vector<int> first,vector<int> second){
+    vector<int> v;
+    int countFirst = 0;
+    int countSecond = 0;
+    int size = first.size()+second.size();
+    int left = 1;
+    for (int i=0; i<size;i++){
+        
+        if(countFirst<first.size() && countSecond<second.size() ){
+            left = (first[countFirst] < second[countSecond]);
+        }
+        else if (countFirst<first.size()) {
+            left = 1;
+        }
+        else{
+            left = 0;
+        }
+        
+        
+        if (left == 1){
+             v.push_back(first[countFirst]);
+            if ( first.size()> countFirst){
+                countFirst+=1;
+            }
+
+        }
+        else{
+                v.push_back(second[countSecond]);
+            if (second.size()> countSecond){
+                countSecond+=1;
+            }
+      
+        }
+        
+    }
+    return v;
+}
+
+
+vector<int> mergeSorting(vector<int> v){
+    if (v.size() <= 1){
+        return v;
+    }
+    vector<int> first(v.cbegin(), v.cbegin()+(v.size()/2));
+    vector<int> second(v.cbegin()+(v.size()/2), v.cend());
+    
+    return merge(mergeSorting(first),mergeSorting(second));
+}
+
+
 vector<int> sort_custom(vector<int> v){
-   int i, j;
-   int n=v.size();
-   for (i = 0; i < n-1; i++){      
-        for (j = 0; j < n-i-1; j++){ 
-           if (v[j] > v[j+1]){
-			   int temp;
-			   temp=v[j];
-			   v[j]=v[j+1];
-			   v[j+1]=temp;
-           }
-	   }
-   }
-   return v;
-}
+    vector<int> sortVec = mergeSorting(v);
+    return sortVec;
+}
+
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