Question

我有一个输入文件，试图从文件中获取一些数据并显示在输出中。

文件中的数据为：

SS
0
NN
1

XX
10
YY
20

和我的代码：

ifstream inFile;
inFile.open("input.txt");

string s1, s3;
int n2, n4;

while ( inFile ) {

    getline(inFile, s1);
    cout << "1: " << s1 << endl;

    inFile >> n2;
    cout << "2: " << n2 << endl;
    inFile.ignore(1000, '\n');

    getline(inFile, s3);
    cout << "3: " << s3 << endl;

    inFile >> n4;
    cout << "4: " << n4 << endl;
    inFile.ignore(1000,'\n');

    cout << endl;
}

检查输出时！输出是：

1: SS
2: 0
3: NN
4: 1

1:
2: 0
3: NN
4: 1

我认为我的问题应该是因为inFile.ignore()。
你能为我解释发生了什么吗？

Answer 1

while ( inFile ) {

  getline(inFile, s1);
  cout << "1: " << s1 << endl;

  inFile >> n2;
  cout << "2: " << n2 << endl;

提取失败时，您正在处理垃圾。

#include <cstdlib>
#include <string>
#include <fstream>
#include <iostream>

int main()
{
    std::ifstream inFile{ "input.txt" };
    if (!inFile.is_open())
        return EXIT_FAILURE;

    std::string s1, s3;
    int n2, n4;

    while (inFile >> s1 >> n2 >> s3 >> n4)
        std::cout << "1: " << s1 << "\n2: " << n2 << "\n3: " << s3 << "\n4: " << n4 << "\n\n";
}

输出：

1: SS
2: 0
3: NN
4: 1

1: XX
2: 10
3: YY
4: 20

如果字符串确实包含空格，并且两个数据集用空行分隔：

#include <limits>

// ...

while (std::getline(inFile, s1) && (inFile >> n2) &&
       inFile.ignore(std::numeric_limits<std::streamsize>::max(), '\n') &&
       std::getline(inFile, s3) && (inFile >> n4))
{
    std::cout << "1: " << s1 << "\n2: " << n2 << "\n3: " << s3 << "\n4: " << n4 << "\n\n";
    inFile.ignore(std::numeric_limits<std::streamsize>::max(), '\n');
    inFile.ignore(std::numeric_limits<std::streamsize>::max(), '\n');
}

C ++-Cin.ignore并从其他文件获取数据

1 个答案:

输出：