Suppose you have an array of floating point numbers with each index into the array being an id number corresponding to some external data structure. You want to sort this array, but in doing so you would destroy the references to the id numbers, since the indexes of the array would no longer correspond to the correct id numbers in the external data structure. For example, let’s say we are dealing with customers of a store and each value in the array is their current balance.
balances = {25.61, 13.45, 89.75, 21.2, 96.50}
Each index in the balances array corresponds to an index in some other array, say:
names = {"Marjory Stewart-Baxter", "Hubert Cumberdale", "Barbara Logan-Price", "Jeremy Fisher", "Mable"}
