如何在C/C++、Python和Java中拆分字符串？

原文:https://www . geesforgeks . org/如何拆分 cc-python-and-java 中的字符串/

用分隔符分割字符串是一项非常常见的任务。例如，我们有一个逗号分隔的文件项目列表，我们想要一个数组中的单个项目。
几乎所有的编程语言，都提供了一个通过某种分隔符来拆分字符串的函数。

In C:

// Splits str[] according to given delimiters.
// and returns next token. It needs to be called
// in a loop to get all tokens. It returns NULL
// when there are no more tokens.
char * strtok(char str[], const char *delims);


C

// A C/C++ program for splitting a string
// using strtok()
#include
#include
int main()
{
    char str[] = "Geeks-for-Geeks";
    // Returns first token
    char *token = strtok(str, "-");
    // Keep printing tokens while one of the
    // delimiters present in str[].
    while (token != NULL)
    {
        printf("%s\n", token);
        token = strtok(NULL, "-");
    }
    return 0;
}


Output: Geeks
for
Geeks


在 C++中

Note: The main disadvantage of strtok() is that it only works for C style strings.
Therefore we need to explicitly convert C++ string into a char array.
Many programmers are unaware that C++ has two additional APIs which are more elegant
and works with C++ string.


方法 1: 使用 C++的 stringstream API

先决条件 : stringstream 原料药

Stringstream 对象可以使用字符串对象进行初始化，它自动 在空格字符上标记字符串。 就像“cin”流 stringstream 让你把一个字符串当成一个单词流来读。

Some of the Most Common used functions of StringStream.
clear() — flushes the stream
str() — converts a stream of words into a C++ string object.
operator <<— pushes a string object into the stream.
operator >> — extracts a word from the stream.


下面的代码演示了它。

C++

#include
using namespace std;
// A quick way to split strings separated via spaces.
void simple_tokenizer(string s)
{
    stringstream ss(s);
    string word;
    while (ss >> word) {
        cout <    }
}
int main(int argc, char const* argv[])
{
    string a = "How do you do!";
    // Takes only space separated C++ strings.
    simple_tokenizer(a);
    cout <    return 0;
}


Output : How
do
you
do!


方法二:使用 C++ find()和 substr()API。

先决条件: 查找功能 和substr()。

这个方法 更健壮，可以用任何分隔符 解析字符串，而不仅仅是空格(虽然默认行为是在空格上分开。)从下面的代码中，逻辑很容易理解。

C++

#include
using namespace std;
void tokenize(string s, string del = " ")
{
    int start = 0;
    int end = s.find(del);
    while (end != -1) {
        cout <        start = end + del.size();
        end = s.find(del, start);
    }
    cout <}
int main(int argc, char const* argv[])
{
    // Takes C++ string with any separator
    string a = "Hi$%do$%you$%do$%!";
    tokenize(a, "$%");
    cout <    return 0;
}


Output: Hi
do
you
do
!


方法三:使用临时管柱

如果给定分隔符的长度为 1，则可以简单地使用临时字符串来拆分字符串。在方法 2 的情况下，这将节省函数开销时间。

C++

#include
using namespace std;
void split(string str, char del){
    // declaring temp string to store the curr "word" upto del
      string temp = "";
      for(int i=0; i<(int)str.size(); i++){
        // If cur char is not del, then append it to the cur "word", otherwise
          // you have completed the word, print it, and start a new word.
         if(str[i] != del){
            temp += str[i];
        }
          else{
            cout <              temp = "";
        }
    }
      cout <}
int main() {
    string str = "geeks_for_geeks";    // string to be split
     char del = '_';    // delimiter around which string is to be split
      split(str, del);
    return 0;
}


Output

geeks for geeks


在 Java 中:
在 Java 中，split()是 String 类中的一个方法。

// expregexp is the delimiting regular expression;
// limit is the number of returned strings
public String[] split(String regexp, int limit);
// We can call split() without limit also
public String[] split(String regexp)


Java 语言(一种计算机语言，尤用于创建网站)

// A Java program for splitting a string
// using split()
import java.io.*;
public class Test
{
    public static void main(String args[])
    {
        String Str = new String("Geeks-for-Geeks");
        // Split above string in at-most two strings 
        for (String val: Str.split("-", 2))
            System.out.println(val);
        System.out.println("");
        // Splits Str into all possible tokens
        for (String val: Str.split("-"))
            System.out.println(val);
    }
}


输出:

Geeks
for-Geeks
Geeks
for
Geeks


Python 中的:
Python 中的 split()方法在用指定的分隔符断开给定的字符串后返回一个字符串列表。

// regexp is the delimiting regular expression;
// limit is limit the number of splits to be made
str.split(regexp = "", limit = string.count(str))


计算机编程语言

line = "Geek1 \nGeek2 \nGeek3"
print(line.split())
print(line.split(' ', 1))


输出:

['Geek1', 'Geek2', 'Geek3']
['Geek1', '\nGeek2 \nGeek3']


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