Write a program that examines a string of characters and determines if all openi

Question

Write a program that examines a string of characters and determines if all opening bracket characters such as (, [, or { are matched with their correct closing characters. Use a stack to do this. The basic algorithm is as follows:

Read the string, character by character.
If the character is an opening bracket character, push its equivalent closing character onto the stack.
If the character is a closing bracket character, pop the stack, and see if the character you popped matches the current character. If not, the brackets in the string are not paired correctly.
If the character is not a bracket character, ignore it.
If you get through the whole string without failing, check to see if the stack is empty. If it is, the brackets are all matched correctly. If not, the brackets were not matched correctly.
Your program should print a message back to the user if the brackets are correctly matched or not

Test your program on some small strings. Once it is working properly, it should work regardless of the string. Try using it on an entire Java source code file.

Explanation / Answer

String processing with character arrays is one of the biggest time-wasters in C. Character arrays require the programmer to keep track of the difference between static quoted strings and arrays created on the stack and the heap, and the fact that sometimes you're passing around a char* and sometimes you must copy the whole array.Especially because string manipulation is so common, character arrays are a great source of misunderstandings and bugs. Despite this, creating string classes remained a common exercise for beginning C++ programmers for many years. The Standard C++ library string class solves the problem of character array manipulation once and for all, keeping track of memory even during assignments and copy-constructions. You simply don't need to think about it.This examines the Standard C++ string class, beginning with a look at what constitutes a C++ string and how the C++ version differs from a traditional C character array. You'll learn about operations and manipulations using string objects, and you'll see how C++strings accommodate variation in character sets and string data conversion.Handling text is one of the oldest programming applications, so it's not surprising that the C++ string draws heavily on the ideas and terminology that have long been used in C and other languages. As you begin to acquaint yourself with C++ strings, this fact should be reassuring. No matter which programming idiom you choose, there are three common things you want to do with a string:

           In C, a string is simply an array of characters that always includes a binary zero (often called the null terminator) as its final array element. There are significant differences between C++ strings and their C progenitors. First, and most important, C++ strings hide the physical representation of the sequence of characters they contain. You don't need to be concerned about array dimensions or null terminators. A string also contains certain “housekeeping” information about the size and storage location of its data. Specifically, a C++ string object knows its starting location in memory, its content, its length in characters, and the length in characters to which it can grow before the string object must resize its internal data buffer. C++ strings thus greatly reduce the likelihood of making three of the most common and destructive C programming errors: overwriting array bounds, trying to access arrays through uninitialized or incorrectly valued pointers, and leaving pointers “dangling” after an array ceases to occupy the storage that was once allocated to it.

           The exact implementation of memory layout for the string class is not defined by the C++ Standard. This architecture is intended to be flexible enough to allow differing implementations by compiler vendors, yet guarantee predictable behavior for users. In particular, the exact conditions under which storage is allocated to hold data for a string object are not defined. String allocation rules were formulated to allow but not require a reference-counted implementation, but whether or not the implementation uses reference counting, the semantics must be the same. To put this a bit differently, in C, every char array occupies a unique physical region of memory. In C++, individual string objects may or may not occupy unique physical regions of memory, but if reference counting avoids storing duplicate copies of data, the individual objects must look and act as though they exclusively own unique regions of storage.

Creating and initializing C++ strings

        Creating and initializing strings is a straightforward proposition and fairly flexible. In the SmallString.cpp example below, the firststring, imBlank, is declared but contains no initial value. Unlike a C char array, which would contain a random and meaningless bit pattern until initialization, imBlank does contain meaningful information. This string object is initialized to hold “no characters” and can properly report its zero length and absence of data elements using class member functions.The next string, heyMom, is initialized by the literal argument “Where are my socks?” This form of initialization uses a quoted character array as a parameter to the string constructor. By contrast, standardReply is simply initialized with an assignment. The last string of the group, useThisOneAgain, is initialized using an existing C++ string object. Put another way, this example illustrates that stringobjects let you do the following:

These are the simplest forms of string initialization, but variations offer more flexibility and control. You can do the following:

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