C++ 如何从文件中读取文本行并将它们放入数组中
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原文地址: http://stackoverflow.com/questions/11546177/
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How to read lines of text from file and put them into an array
提问by newbieprogrammer
I created a text file love.txt:
我创建了一个文本文件love.txt：
i love you
you love me
How do I store them into separate array, namely line1and line2and then display them out in console?
如何将它们存储在独立的阵列，即line1和line2，然后在控制台显示出来？
#include <iostream>
#include <fstream>
#include <string>
using namespace std;
int main()
{
string line1[30];
string line2[30];
ifstream myfile("love.txt");
int a = 0;
int b = 0;
if(!myfile)
{
cout<<"Error opening output file"<<endl;
system("pause");
return -1;
}
while(!myfile.eof())
{
getline(myfile,line1[a],' ');
cout<<"1."<<line1[a]<<"\n";
getline(myfile,line2[b],' ');
cout<<"2."<<line2[b]<<"\n";
}
}
回答by Mahesh Meniya
Try specifying the last argument as '\n' in both getline()functions:
尝试在两个函数中将最后一个参数指定为'\n'getline()：
getline(myfile, line1[a], '\n');
instead of
代替
getline(myfile, line1[a], ' ');
回答by Attila
You can think of a string as an array of characters, so you will only need one array of strings:
您可以将字符串视为字符数组，因此您只需要一个字符串数组：
const size_t SIZE = 30;
string line[SIZE]; // creates SIZE empty strings
size_t i=0;
while(!myfile.eof() && i < SIZE) {
getline(myfile,line[i]); // read the next line into the next string
++i;
}
for (i=0; i < SIZE; ++i) {
if (!line[i].empty()) { // print only if there is something in the current line
cout << i << ". " << line[i];
}
}
You could maintain a counter to see how many lines you have stored into (instead of checking for empty lines) as well -- this way you will properly print empty lines as well:
您也可以维护一个计数器来查看您存储了多少行（而不是检查空行）——这样您也可以正确打印空行：
const size_t SIZE = 30;
string line[SIZE]; // creates SIZE empty strings
size_t i=0;
while(!myfile.eof() && i < SIZE) {
getline(myfile,line[i]); // read the next line into the next string
++i;
}
size_t numLines = i;
for (i=0; i < numLines; ++i) {
cout << i << ". " << line[i]; // no need to test for empty lines any more
}
Note: you will be able to store only up to SIZElines. If you need more, you will have to increase SIZEin the code. Later on you will learn about std::vector<>that allows you to dynamically grow the size as needed (so you won't need to keep track of how many you stored).
注意：您最多只能存储SIZE行。如果需要更多，则必须增加SIZE代码。稍后您将了解std::vector<>它允许您根据需要动态增加大小（因此您无需跟踪存储的数量）。
Note: the use of constants like SIZEallows you to change the size in one place only
注意：使用常量 likeSIZE允许您仅在一处更改大小
Note: you should add a check for errors in the input stream on top of eof(): in case there was a read failure other than reaching the end of the file:
注意：您应该在输入流中添加对错误的检查eof(): 以防读取失败而不是到达文件末尾：
while (myfile && ...) {
// ...
}
here myfileis converted to a boolean value indicating if it is OK to use it (true) or not (false)
heremyfile转换为布尔值，指示是否可以使用 ( true) 或不使用 ( false)
Update:
更新：
I just realized what you are after: you want to read the input as series of words (separated by space), but display them as lines. In this case, you will need arrays-of-arrays to store each line
我刚刚意识到您在追求什么：您想将输入读取为一系列单词（以空格分隔），但将它们显示为行。在这种情况下，您将需要数组数组来存储每一行
string line[SIZE1][SIZE2];
where SIZE1is the maximum amount of lines you can store and SIZE2is the maximum amount of words you can store per line
其中SIZE1是您可以存储SIZE2的最大行数，是每行可以存储的最大单词数
Filling this matrix will be more complex: you will need to read the input line-by-line then separate the words within the line:
填充这个矩阵会更复杂：您需要逐行读取输入，然后将行内的单词分开：
string tmp; // temporary string to store the line-as-string
getline(myfile, tmp);
stringstream ss(tmp); // convert the line to an input stream to be able to extract
// the words
size_t j=0; // the current word index
while (ss) {
ss >> line[i][j]; // here i is as above: the current line index
++j;
}
Output:
输出：
for (i=0; i < numLines; ++i) {
cout << i << ". ";
for (size_t j=0; j < SIZE2; ++j) {
if (!line[i][j].empty()) {
cout << line[i][j] << " ";
}
}
}
回答by edrianhadinata
How about this.. .
这个怎么样.. 。
vector <string> v;
string line;
ifstream fin("love.txt");
while(getline(fin,line)){
v.push_back(line);
}
