Can you please suggest an algorithm that uses pointers and I also have to read and save the text file, which I#m having trouble with. Here is a rough translation of the task into English(I used google translator so it's bit jumbled, my german's not that good):
Define a structure with two pointers to strings for each of the cities and the additional info. Set your internal memory for the data field with 100,000 array elements that are of this type of structure. Use the zip code as an index, for example, are stored in the array element with index [47 057] is a pointer to the string "Duisburg" and a null pointer for the addition or in the array element with index [45 472] is a pointer to the string "Mülheim" for the place and a pointer to the string "at the Ruhr for the addition. You needn't disk space, may be applied to places that are available with several postal codes, create their own strings for the name of the place and the additional info. The advantage of using such a field is that when you sort reading the data virtually to the zip code in time O (n) (this sorting method is called multiple distributors) and the search for data in super-fast constant time O (1) takes place.