This tip demonstrates how to add an element to a particular position in an array and how to shift all elements in and above that position up one position.

Using subscripts:

-------------------void insert(int a[], int& n, int maxsize, int index, int key) {   // function:   //    Inserts key at a[index], shifting other values up as necessary.   //    Updates number of elements in a.   // parameters:   //    a       inout  array of values.   //    n       inout  number of values in a, a[0]..a[n-1]   //    maxsize in     maximum number of elements that can fit in a   //    index   in     position to insert at   //    key     in     value to insert.   // returns: nothing   if (index < 0 || index > maxsize-1) {      ; // ERROR - return special value, halt, throw exception, or expandarray.   }   // Move all elements up one position.  i is destination.   for (int i=n; i>index; i--) {       a[i] = a[i-1];   }   a[index] = key;  // put value in vacated position   n++;             // update count of items in a   return;}

Using pointers:

----------------void insert(int* a, int& n, int maxsize, int index, int key) {   if (index < 0 || index > maxsize-1) {      ;// ERROR - return special value, halt, throw exception, or expandarray.   }   int* dest = a+index;   int* tail = a+n;   while (tail > dest) {       *tail = *(tail-1);       tail--;   }   *dest = key;  // put value in vacated position   n++;          // update count of items in a   return;}