Question

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如何将数据读入三个字符串数组？第一列进入第一个字符串数组，第二列进入第二个字符串数组，第三列进入第三个字符串数组。这是我试过的代码，但是最后一个数组就行了。

#include <iostream>
#include <string>
#include <sstream>
#include <fstream>

using namespace std;
 int main(){
    //load the text file and put it into a single string:
    std::ifstream in("test.txt");
    std::stringstream buffer;
    buffer << in.rdbuf();
    std::string test = buffer.str();
    std::cout << test << std::endl << std::endl;

//create variables that will act as "cursors". we'll take everything between them.
size_t pos1 = 0;
size_t pos2;

//create the array to store the strings.
std::string str[5];
std::string str2[5];
std::string str3[5];

int x;
int y;

for(y=0; y<5;y++){



    for ( x=0; x<3; x++){

        pos2 = test.find(" ", pos1); //search for the bar "|". pos2 will be where the bar was found.

       if(x==0){

        str[y] = test.substr(pos1, (pos2-pos1)); //make a substring, wich is nothing more 

       }else if(x==1){

        str2[y] = test.substr(pos1, (pos2-pos1)); //make a substring, wich is nothing more 


       }else if(x==2){

        str3[y] = test.substr(pos1, (pos2-pos1)); //make a substring, wich is nothing more 


       }                                       //than a copy of a fragment of the big string.
      //  std::cout << str[x] << std::endl;
       // std::cout << "pos1:" << pos1 << ", pos2:" << pos2 << std::endl;
        pos1 = pos2+1; // sets pos1 to the next character after pos2. 
                         //so, it can start searching the next bar |.




    }



}

for (int p=0; p<5; p++){

    cout << str[p] <<endl;
    cout << str2[p] <<endl;
    cout << str3[p] <<endl;

}


    return 0;


 }

Answer 1

如果考虑到非常大的文件，将整个文件放在一个字符串中效率非常低。

你想要实现的目标并不像你期望的那样复杂（至少在c ++中）。你可以这样做：

for(size_t ind = 0; ind < 5; ++ind)
    in >> str[ind] >> str2[ind] >> str3[ind];

Answer 2

我以不同的方式尝试了，让我们理解下面的简单代码。

while(in.good())
{
string stri;
int i=1,a=0,b=0,c=0;
in >> stri;

switch(i%3) {
case 1:
str[a]=stri;
a++;
break;
case 2:
str2[b]=stri;
b++;
break;
case 3:
str3[c]=stri;
c++;
break;
}
i++;

}

此处变量a，b和c计算数组索引。每个循环，它计算(i%3)并填充正确的数组。

代码可能有一些问题，这只是为了想法。我甚至没有测试过它。

注意当且仅当您有3列时，此代码才有效。

如何从文件中读取特定数据到数组字符串

2 个答案: