C++ 使用stringstream从混合字符串中提取数字
我正在尝试使用stringstream从字符串中提取数字,如Hello1234。我已经编写了一段代码,用于在输入时从字符串中提取数字,如: 你好1234世界9876你好1234 将12349876作为输出 但它不会读取同时包含字符串和数字的混合字符串。我们如何提取它? -例如:Hello1234应该给出1234 以下是我到目前为止的代码:C++ 使用stringstream从混合字符串中提取数字,c++,C++,我正在尝试使用stringstream从字符串中提取数字,如Hello1234。我已经编写了一段代码,用于在输入时从字符串中提取数字,如: 你好1234世界9876你好1234 将12349876作为输出 但它不会读取同时包含字符串和数字的混合字符串。我们如何提取它? -例如:Hello1234应该给出1234 以下是我到目前为止的代码: cout << "Welcome to the string stream program. " << endl; strin
cout << "Welcome to the string stream program. " << endl;
string string1;
cout << "Enter a string with numbers and words: ";
getline(cin, string1);
stringstream ss; //intiazling string stream
ss << string1; //stores the string in stringstream
string temp; //string for reading words
int number; //int for reading integers
while(!ss.eof()) {
ss >> temp;
if (stringstream(temp) >> number) {
cout << "A number found is: " << number << endl;
}
}
cout编号){
cout如果您不局限于使用std::stringstream
的解决方案,我建议您看看。示例:
int main() {
std::string s = "Hello 123 World 456 Hello789";
std::regex regex(R"(\d+)"); // matches a sequence of digits
std::smatch match;
while (std::regex_search(s, match, regex)) {
std::cout << std::stoi(match.str()) << std::endl;
s = match.suffix();
}
}
在进行流提取之前,只需将字符串中的任何字符替换为空白即可
std::string str = "Hello 1234 World 9876 Hello1234";
for (char& c : str)
{
if (isalpha(c))
c = ' ';
}
std::stringstream ss(str);
int val;
while (ss >> val)
std::cout << val << "\n";
您可以将下面的代码与任何类型的流一起使用—stringstream
。它从流读取到第一个数字。数字放回流中,然后像通常一样读取数字
添加我的版本:
#包括
#包括
#包括
int main(){
std::字符串s;
标准::getline(标准::cin,s);
std::stringstream-ss;
整数;
用于(常量字符c:s){
if(std::isdigit(static_cast(c)){//多亏了Aconcagua
ss>数量){
std::cout编号)
{
std::cout问题本身非常琐碎,作为程序员,我们大多数人每天都在解决这类问题。我们知道,对于任何给定的问题,都有很多解决方案,但作为程序员,我们试图找出任何给定问题的最佳解决方案
当我遇到这个问题时,已经有很多有用且正确的答案,但为了满足我的好奇心,我尝试对所有其他解决方案进行基准测试,以找出最佳的解决方案
我找到了上面最好的一个,觉得还有一些改进的空间
所以我在这里发布了我的解决方案和基准代码
#include <chrono>
#include <iostream>
#include <regex>
#include <sstream>
#include <string>
#include <vector>
using namespace std;
#define REQUIER_EQUAL(x, y) \
if ((x) != (y)) { \
std::cout << __PRETTY_FUNCTION__ << " failed at :" << __LINE__ \
<< std::endl \
<< "\tx:" << (x) << "\ty:" << (y) << std::endl; \
; \
}
#define RUN_FUNCTION(func, in, out) \
auto start = std::chrono::system_clock::now(); \
func(in, out); \
auto stop = std::chrono::system_clock::now(); \
std::cout << "Time in " << __PRETTY_FUNCTION__ << ":" \
<< std::chrono::duration_cast<std::chrono::microseconds>(stop - \
start) \
.count() \
<< " usec" << std::endl;
//Solution by @Evg
void getNumbers1(std::string input, std::vector<int> &output) {
std::regex regex(R"(\d+)"); // matches a sequence of digits
std::smatch match;
while (std::regex_search(input, match, regex)) {
output.push_back(std::stoi(match.str()));
input = match.suffix();
}
}
//Solution by @n314159
void getNumbers2(std::string input, std::vector<int> &output) {
std::stringstream ss;
int number;
for (const char c : input) {
if (std::isdigit(static_cast<unsigned char>(c))) { // Thanks to Aconcagua
ss << c;
} else if (ss >> number) {
output.push_back(number);
}
}
}
//Solution by @The Failure by Design
void getNumbers3(std::string input, std::vector<int> &output) {
istringstream is{input};
char c;
int n;
while (is.get(c)) {
if (!isdigit(static_cast<unsigned char>(c)))
continue;
is.putback(c);
is >> n;
output.push_back(n);
}
}
//Solution by @acraig5075
void getNumbers4(std::string input, std::vector<int> &output) {
for (char &c : input) {
if (isalpha(c))
c = ' ';
}
std::stringstream ss(input);
int val;
while (ss >> val)
output.push_back(val);
}
//Solution by me
void getNumbers5(std::string input, std::vector<int> &output) {
std::size_t start = std::string::npos, stop = std::string::npos;
for (auto i = 0; i < input.size(); ++i) {
if (isdigit(input.at(i))) {
if (start == std::string::npos) {
start = i;
}
} else {
if (start != std::string::npos) {
output.push_back(std::stoi(input.substr(start, i - start)));
start = std::string::npos;
}
}
}
if (start != std::string::npos)
output.push_back(std::stoi(input.substr(start, input.size() - start)));
}
void test1_getNumbers1() {
std::string input = "Hello 123 World 456 Hello789 ";
std::vector<int> output;
RUN_FUNCTION(getNumbers1, input, output);
REQUIER_EQUAL(output.size(), 3);
REQUIER_EQUAL(output[0], 123);
REQUIER_EQUAL(output[1], 456);
REQUIER_EQUAL(output[2], 789);
}
void test1_getNumbers2() {
std::string input = "Hello 123 World 456 Hello789";
std::vector<int> output;
RUN_FUNCTION(getNumbers2, input, output);
REQUIER_EQUAL(output.size(), 3);
REQUIER_EQUAL(output[0], 123);
REQUIER_EQUAL(output[1], 456);
REQUIER_EQUAL(output[2], 789);
}
void test1_getNumbers3() {
std::string input = "Hello 123 World 456 Hello789";
std::vector<int> output;
RUN_FUNCTION(getNumbers3, input, output);
REQUIER_EQUAL(output.size(), 3);
REQUIER_EQUAL(output[0], 123);
REQUIER_EQUAL(output[1], 456);
REQUIER_EQUAL(output[2], 789);
}
void test1_getNumbers4() {
std::string input = "Hello 123 World 456 Hello789";
std::vector<int> output;
RUN_FUNCTION(getNumbers4, input, output);
REQUIER_EQUAL(output.size(), 3);
REQUIER_EQUAL(output[0], 123);
REQUIER_EQUAL(output[1], 456);
REQUIER_EQUAL(output[2], 789);
}
void test1_getNumbers5() {
std::string input = "Hello 123 World 456 Hello789";
std::vector<int> output;
RUN_FUNCTION(getNumbers5, input, output);
REQUIER_EQUAL(output.size(), 3);
REQUIER_EQUAL(output[0], 123);
REQUIER_EQUAL(output[1], 456);
REQUIER_EQUAL(output[2], 789);
}
int main() {
test1_getNumbers1();
// test1_getNumbers2();
test1_getNumbers3();
test1_getNumbers4();
test1_getNumbers5();
return 0;
}
如果您想使用stringstream,可以迭代string1
,将每个数字或空格字符添加到ss
,然后提取数字。使用get
逐个获取字符。读取数字后,使用putback
将其放回流中,然后像读取数字一样读取数字RMALY do:ss>>n
@ZDFpeek
+ignore
可能是更好的选择…@Aconcagua我认为它是等效的,只是更多的行。@ZDF因为我们需要一个else分支?也许……我个人更喜欢在需要之前不修改对象。不过,在我看来,从流中提取一个字符,然后将其放回是等效的如果不需要的话,可以将一个对象推到一个向量中,然后再次移除,而偷看则对应于第一次检查,如果需要的话,只推一次。承认,流上的开销要少得多…对于“Hello1234World9876Hello1234”来说,这不会失败吗
?@Evg是的。也许OP可以用更多的例子来阐明要求。也许只是不删除,而是替换为空格?为了完全安全,应该将isalpha
的参数转换为unsigend(请参阅)。为了完全安全,isdigit
需要将字符转换为unsigned(请参阅)@Aconcagua我错过了这一条-谢谢。对目前的情况来说可能不重要。同意,但最好从一开始就习惯,否则人们可能会忘记什么时候需要,然后被咬;)@Aconcagua改变了。:o)刚刚发现:“[…]只有更多的行”–实际上更少:while((c=is.peek())!=std::istream::traits_type::eof(){if(isdigit)return是>>n;is.ignore();}
–但是while条件很难看;)为了完全安全,isdigit
需要将字符转换为无符号字符(请参见)。@n314159是否运行过此代码?我尝试了gcc(Ubuntu 7.4.0-1ubuntu1~18.04.1)7.4.0
没有给出任何输出。我确实给出了。但是再看一遍,如果字符串以最后一个数字结尾,似乎不会输出最后一个数字。我将稍后再试。@ManthanTilva修复了它。这不是一个有效的测试。更改测试调用的顺序,您将得到不同的结果。这是我得到的:测试1中的时间\u getNumbers5:7 usec测试中的时间1\u GetNumbers 1:62 usec测试中的时间1\u GetNumbers 4:21 usec测试中的时间3:4 usec
加上:您的代码没有流
-请参阅问题标题。OP不是要求快速解决方案,而是要求解决方案。@TheFailurebyDesign,只是通过重新排序进行检查。您是对的。知道原因吗?如何克服此问题?缓存,可能请尝试分别运行每个测试。
#include <iostream>
using namespace std;
istream& get_number( istream& is, int& n )
{
while ( is && !isdigit( static_cast<unsigned char>( is.get() ) ) )
;
is.unget();
return is >> n;
}
int main()
{
int n;
while ( get_number( cin, n ) )
cout << n << ' ';
}
const char* get_number( const char*& s, int& n )
{
// end of string
if ( !*s )
return 0;
// skip to first digit
while ( !isdigit( static_cast<unsigned char>( *s ) ) )
++s;
// convert
char* e;
n = strtol( s, &e, 10 );
return s = e;
}
//...
while ( get_number( s, n ) )
//...
#include <chrono>
#include <iostream>
#include <regex>
#include <sstream>
#include <string>
#include <vector>
using namespace std;
#define REQUIER_EQUAL(x, y) \
if ((x) != (y)) { \
std::cout << __PRETTY_FUNCTION__ << " failed at :" << __LINE__ \
<< std::endl \
<< "\tx:" << (x) << "\ty:" << (y) << std::endl; \
; \
}
#define RUN_FUNCTION(func, in, out) \
auto start = std::chrono::system_clock::now(); \
func(in, out); \
auto stop = std::chrono::system_clock::now(); \
std::cout << "Time in " << __PRETTY_FUNCTION__ << ":" \
<< std::chrono::duration_cast<std::chrono::microseconds>(stop - \
start) \
.count() \
<< " usec" << std::endl;
//Solution by @Evg
void getNumbers1(std::string input, std::vector<int> &output) {
std::regex regex(R"(\d+)"); // matches a sequence of digits
std::smatch match;
while (std::regex_search(input, match, regex)) {
output.push_back(std::stoi(match.str()));
input = match.suffix();
}
}
//Solution by @n314159
void getNumbers2(std::string input, std::vector<int> &output) {
std::stringstream ss;
int number;
for (const char c : input) {
if (std::isdigit(static_cast<unsigned char>(c))) { // Thanks to Aconcagua
ss << c;
} else if (ss >> number) {
output.push_back(number);
}
}
}
//Solution by @The Failure by Design
void getNumbers3(std::string input, std::vector<int> &output) {
istringstream is{input};
char c;
int n;
while (is.get(c)) {
if (!isdigit(static_cast<unsigned char>(c)))
continue;
is.putback(c);
is >> n;
output.push_back(n);
}
}
//Solution by @acraig5075
void getNumbers4(std::string input, std::vector<int> &output) {
for (char &c : input) {
if (isalpha(c))
c = ' ';
}
std::stringstream ss(input);
int val;
while (ss >> val)
output.push_back(val);
}
//Solution by me
void getNumbers5(std::string input, std::vector<int> &output) {
std::size_t start = std::string::npos, stop = std::string::npos;
for (auto i = 0; i < input.size(); ++i) {
if (isdigit(input.at(i))) {
if (start == std::string::npos) {
start = i;
}
} else {
if (start != std::string::npos) {
output.push_back(std::stoi(input.substr(start, i - start)));
start = std::string::npos;
}
}
}
if (start != std::string::npos)
output.push_back(std::stoi(input.substr(start, input.size() - start)));
}
void test1_getNumbers1() {
std::string input = "Hello 123 World 456 Hello789 ";
std::vector<int> output;
RUN_FUNCTION(getNumbers1, input, output);
REQUIER_EQUAL(output.size(), 3);
REQUIER_EQUAL(output[0], 123);
REQUIER_EQUAL(output[1], 456);
REQUIER_EQUAL(output[2], 789);
}
void test1_getNumbers2() {
std::string input = "Hello 123 World 456 Hello789";
std::vector<int> output;
RUN_FUNCTION(getNumbers2, input, output);
REQUIER_EQUAL(output.size(), 3);
REQUIER_EQUAL(output[0], 123);
REQUIER_EQUAL(output[1], 456);
REQUIER_EQUAL(output[2], 789);
}
void test1_getNumbers3() {
std::string input = "Hello 123 World 456 Hello789";
std::vector<int> output;
RUN_FUNCTION(getNumbers3, input, output);
REQUIER_EQUAL(output.size(), 3);
REQUIER_EQUAL(output[0], 123);
REQUIER_EQUAL(output[1], 456);
REQUIER_EQUAL(output[2], 789);
}
void test1_getNumbers4() {
std::string input = "Hello 123 World 456 Hello789";
std::vector<int> output;
RUN_FUNCTION(getNumbers4, input, output);
REQUIER_EQUAL(output.size(), 3);
REQUIER_EQUAL(output[0], 123);
REQUIER_EQUAL(output[1], 456);
REQUIER_EQUAL(output[2], 789);
}
void test1_getNumbers5() {
std::string input = "Hello 123 World 456 Hello789";
std::vector<int> output;
RUN_FUNCTION(getNumbers5, input, output);
REQUIER_EQUAL(output.size(), 3);
REQUIER_EQUAL(output[0], 123);
REQUIER_EQUAL(output[1], 456);
REQUIER_EQUAL(output[2], 789);
}
int main() {
test1_getNumbers1();
// test1_getNumbers2();
test1_getNumbers3();
test1_getNumbers4();
test1_getNumbers5();
return 0;
}
Time in void test1_getNumbers1():703 usec
Time in void test1_getNumbers3():17 usec
Time in void test1_getNumbers4():10 usec
Time in void test1_getNumbers5():6 usec