[C++] STL container - string string operation ⑧ (string string related algorithm | string conversion - std::transform function | string flip - std::reverse function)

1. String string conversion - std::transform function

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1. std::transform function prototype description

The C++ std::transform function is a general algorithm in the <algorithm> header file, used to convert elements within a specified range;

stdtransformThe function in the command space is used to convert the contents of the specified range of the STL container;

According to the provided parameters, this function can extract characters from the source string, convert them according to the specified format, and then return a new string;

template< class InputIt, class OutputIt, class UnaryOperation >  
OutputIt transform( InputIt first, InputIt last, OutputIt d_first, UnaryOperation unary_op );  
  
template< class InputIt1, class InputIt2, class OutputIt, class BinaryOperation >  
OutputIt transform( InputIt1 first1, InputIt1 last1, InputIt2 first2, OutputIt d_first, BinaryOperation binary_op );

Parameter Description :

• first: the starting iterator of the input range, indicating the range of elements to be converted;
• last: the terminal iterator of the input range, indicating the range of elements to be converted;
• d_first: the starting iterator of the output range, indicating the range in which the converted elements should be written;
• unary_op unary operation function object: used to convert each element in the input range;
• binary_op binary operation function object: used to combine and convert elements in input range 1 with elements in input range 2;

Operation function object:

• toupper: Convert string to uppercase letters;
• tolower: Convert the string to lowercase letters;

2. Code example - string class transform function conversion

Code example:

#include "iostream"
using namespace std;
#include "string"
#include "algorithm"

int main() {
    
    

	string s1 = "Tom And Jerry";

	// 将字符串转为大写字母
	transform(s1.begin(), s1.end(), s1.begin(), toupper);
	// 打印 s1值
	cout << "s1 = " << s1 << endl;

	// 将字符串转为小写字母
	transform(s1.begin(), s1.end(), s1.begin(), tolower);
	// 打印 s1值
	cout << "s1 = " << s1 << endl;


	// 控制台暂停 , 按任意键继续向后执行
	system("pause");

	return 0;
};

Results of the :

s1 = TOM AND JERRY
s1 = tom and jerry
Please press any key to continue. . .

2. String string flip - std::reverse function

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1. std::reverse function prototype description

std::reverseis an algorithmic function in the <algorithm> header file, used to reverse the order of elements within a given STL container range;

std::reverseFunction prototype:

template< class BidirectionalIt >  
void reverse( BidirectionalIt first, BidirectionalIt last );

Parameter Description:

• first : A bidirectional iterator pointing to the starting element of the range to be reversed;
• last : A bidirectional iterator pointing to the terminating element of the range to reverse;

2. Code example - std::reverse function

Code example:

#include "iostream"
using namespace std;
#include "string"
#include "algorithm"

int main() {
    
    

	string s1 = "Tom And Jerry";

	// 将字符串 翻转
	reverse(s1.begin(), s1.end());
	// 打印 s1值
	cout << "s1 = " << s1 << endl;


	// 控制台暂停 , 按任意键继续向后执行
	system("pause");

	return 0;
};

Results of the :

s1 = yrreJ dnA moT
Please press any key to continue. . .