change implementation to insertion-sort

sorting.cpp

-#include<iostream>
-#include "sorting.h"
+#include"sorting.h"
 using namespace std;
 
-vector<int> sort_custom(vector<int> v1){
-   int i, j;
-   int n=v1.size();
-   for (i = 0; i < n-1; i++) {   
-       for (j = 0; j < n-i-1; j++){ 
-           if (v1[j] > v1[j+1])
-              swap(v1[j], v1[j+1]);
+vector<int> sort_custom( vector<int> a ){
+	int i, key, j;
+	int n=a.size();
+   for (i = 1; i < n; i++)
+   {
+       key = a[i];
+       j = i-1;
+
+       while (j >= 0 && a[j] > key)
+       {
+           a[j+1] = a[j];
+           j = j-1;
        }
+       a[j+1] = key;
    }
-    return v1;    
+   return a;
 }
+
+