[英]How to read specific data from file into array string
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如何将数据读入三个字符串数组? 第一列进入第一字符串数组,第二列进入第二字符串数组,第三列进入第三字符串数组。 这是我尝试过的代码,但是最后一个数组进入了一行。
#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;
}
如果您考虑的是大文件,则将整个文件放在一个字符串中可能效率很低。
您要实现的目标实际上并没有您预期的那么复杂(至少在c ++中如此)。 您可以这样做:
for(size_t ind = 0; ind < 5; ++ind)
in >> str[ind] >> str2[ind] >> str3[ind];
我以其他方式尝试过,让我们了解下面的简单代码。
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++;
}
在这里,变量a
, b
和c
计算数组索引。 每个循环都会计算(i%3)
并填充正确的数组。
代码可能存在一些问题,这只是出于想法。 我什至没有测试。
注意 ,只有当您有3列时,此代码才有效。
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