Programming conversion between character and integers
A code that transforms a character (such as 5) to a numerical representation expressed as an integer (such as 5) is a typical programming exercise. Every character can be represented as an underlying number which in the majority of cases is ASCII or Unicode that can be utilized as the base of this conversion.
C Language
C has three major ways of converting a character into an integer.
Based on ASCII Values: Every character in the C language has a distinctive numerical value known as the ASCII value. That is, their ASCII values are consecutive with numeric characters ('0 to '9'). In order to obtain the integer representation of a numeric character you just do the difference between the ASCII value of 0 and the ASCII value of the character. example int N = (ch - '0');, transforms the character ch into an integer N. The time and space complexity of this method are O (1).
Through sscanf() Function: sscanf() function enables a formatted string input to be read. It has the power to change a character to an integer by converting the character as a string and reading it on the %d format specifier. The time as well as space complexity of this method is O(1).
Using atoi() Function: atoi() function which is under the C standard library <stdlib.h> is intended to convert a series of digits into an integer. It is used to convert a string but it is usually related to strings when it comes to the matter of conversion. The time and space complexity of this method is O(1) too.
C++ Language
Just like C, C++ has several approaches to convert a character to an integer. When C++ uses the numeric operations directly on the characters, which will be used in the representation of the numeric values, then the program will interpret the ASCII value of the character rather than the numeric. Thus, there is a need to convert.
Application of ASCII Code Conversion: C++ Function On utilization of ASCII code conversion, the ASCII code is 48, 49, and so on till 9 of ASCII value of 0, 1 respectively using the above code. As mentioned above, by simply subtracting the character 0 with any digit character, one can convert it into an integer. In this approach they both are operated on their ASCII values. Instead, we can imbue the character with integer type and then add 0 in the same manner, which will also convert the character to the integer value.
ATOI () Function: The atoi() Function in the C++ language can also be used to convert a character with the argument being a pointer to a character type. With the similarity to stoi() (string to int), atoi() belongs to C and accepts character arrays, and stoi() deals with strings. In case the string cannot be converted to integer atoi() returns 0 whereas in the case of stoi() an exception is raised.
Conversion with the help of static_cast: static_cast is a C++ method of conversions between variables of different types. It does not need any special library.
Function sscanf(): The sscanf() in C++ is applied on a character array and transforms the array to an integer without utilizing the ASCII codes. It scans through its parameter that is a character array (a pointer) and returns its value converted to the required data type. In the event that the values inside the character array are not integers or they would fail to be converted, the outcome will take the shape of a garbage value. When it starts with the integer values then followed by the non-integer values, only the initial integer values are converted.
The method with stringstream: the stringstream is a C++ stream whose class is based on iostream but whose connection relates the string object and a stream and with which you can be directed to a stream of a string. The class is helpful when processing input and it necessitates the inclusion of the header file. Its non-convertible string behavior is analogous to sscanf(), except returning zero upon lack of beginner integer values.
Java Language
There are some techniques available in Java on how to convert character to integer.
Implicit Type Casting: The character can be assigned to the variable whose declared type is an integer and The character will be implicitly turned into its ASCII code. To give an example, the code 5 taken as a character will be stored in an integer variable as 53 which is the ASCII code of 5.
Subtracting 0: The easiest way of doing it is by subtracting the numerical character 0 (zero) by the character in question. This is applicable since character arithmetic operates on the ASCII internally. To take one example, char ch1 = '5'; int num1 = ch1 - '0'; would convert '5' into a 5 since the value of '5' (in ASCII) minus the value of '0' (in ASCII), is 5.
Character.getNumericValue() Method: A Character class in Java offers getNumericValue() method, the value of which is an integer number representing encoding of Unicode character. The given method uses the character as input and outputs the associated integer value.
Integer.parseInt() and String.valueOf(): In this method one takes a character data and converts it into a String using String.valueOf(), and then converts the String in an int using Integer.parseInt(). The member function valueOf() belongs to a String class whereas parseInt() belongs to an Integer class.
Python Language
Characters in Python are in most cases handled as strings where they are usually converted to integer values by taking their Unicode (or ASCII) equivalent.
Using ord() Function: The ord() function in Python changes a given character to the corresponding Unicode integer value. This function is a very simplified and efficient tool for this operation. As an example, ord('a') will give 97, which is the ASCII code of 'a'.
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