add API and data read

main.cpp

+#include <iostream>
+#include "sorting.h"
+using namespace std;
+
+int main()
+{
+    int n; cin>>n;
+    vector<int> v(n);
+    
+    for(int i = 0; i < n; i++) cin >> v[i];
+    v = sort_custom(v);
+    for(int i = 0; i < n; i++) cout << v[i] << " ";
+    cout<<endl;
+    return 0;
+}
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sorting.h

+#include <vector>
+using namespace std; 
+vector<int> sort_custom(vector<int> a);
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