正在替換字串的第一次出現，如何替換所有出現的字串？

我已經用loop replace構建了基本結構，在C 中str.replace只是替換單個字串，但是，在某些情況下，我們需要替換所有相同的字串，我的代碼可以編譯成功并且可以輸出到螢屏，但似乎沒有替換成功。

提前致謝

這是我的代碼：

#include <iostream>
#include <fstream>
#include <string>
int main(void)
{
    // initialize
    std::ofstream fout;
    std::ifstream fin;
    fout.open("cad.dat");
    fout <<  "C is a Computer Programming Language which is used worldwide, Everyone should learn how to use C" << std::endl;

    fin.open("cad.dat");
    std::string words;
    getline(fin,words);
    std::cout << words << std::endl;
 
    while(1)
    {
        std::string::size_type pos(0);
        if (pos = words.find("C") != std::string::npos && words[pos 1] != ' ') //the later one is used to detect the single word "C"
        {
            words.replace(pos, 1, "C  "); 
        }
        else
        {
            break;
        }
    }

    std::cout << words;
}

uj5u.com熱心網友回復：

您可以通過如下方式簡化您的程式regex：

std::regex f("\\bC\\b");
words = std::regex_replace(words, f, "C  "); // replace "C" with "C  "

然后就不需要while 回圈，如下面的程式所示：

#include <iostream>
#include <fstream>
#include <regex>
#include <string>
int main(void)
{
    // initialize
    std::ofstream fout;
    std::ifstream fin;
    fout.open("cad.dat");
    fout <<  "C is a Computer Programming Language which is used worldwide, Everyone should learn how to use C" << std::endl;

    fin.open("cad.dat");
    std::string words;
    getline(fin,words);
    std::cout << words << std::endl;
 
    std::regex f("\\bC\\b");
    words = std::regex_replace(words, f, "C  "); // replace "C" with "C  "

    std::cout << words;
}

uj5u.com熱心網友回復：

您需要保存pos并將其用于以下find操作，但您當前將其初始化為0回圈中的每次迭代while。

你可以while用這個替換 while回圈，例如：

for(std::string::size_type pos = 0;
    (pos = words.find("C", pos)) != std::string::npos; // start find at pos
    pos  = 1)  // skip last found "C"
{
    if(pos   1 == words.size() || words[pos   1] == ' ')
        words.replace(pos, 1, "C  ");
}

注意：這將替換C以Ctoo結尾的in 單詞，例如首字母縮略詞 likeC2C將變為C2C 。此外，C.不會處理以 結尾的句子。要處理這些情況，您也可以在發現之前添加對字符的檢查，C并在檢查中添加標點符號。

例子：

#include <cctype>   // isspace, ispunct
#include <iostream>
#include <string>

int main()
{
    std::string words = "C Computer C2C C. I like C, because it's C";
    std::cout << words << '\n';

    // a lambda to check for space or punctuation characters:
    auto checker = [](unsigned char ch) {
        return std::isspace(ch) || std::ispunct(ch);
    };

    for(std::string::size_type pos = 0;
        (pos = words.find("C", pos)) != std::string::npos;
        pos  = 1)
    {
        if( (pos == 0 || checker(words[pos - 1])) &&
            (pos   1 == words.size() || checker(words[pos   1]))
        ) {
            words.replace(pos, 1, "C  ");
        }
    }

    std::cout << words << '\n';
}

輸出：

C Computer C2C C. I like C, because it's C
C   Computer C2C C  . I like C  , because it's C  

標籤：C 细绳 代替

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