std :: cin和scanf()之间的区别应用于字符串 [英] Difference between std::cin and scanf() applied to string

问题描述

我正在尝试将字符串的第一个字符写入char类型的变量.使用std :: cin(注释掉)可以正常工作，但是使用scanf()会出现运行时错误.当我输入"LLUUUR"时，它会粉碎.为什么会这样呢?使用MinGW.

I am trying to get the first character of a string written to a variable of type char. With std::cin (commented out) it works fine, but with scanf() I get runtime error. It crushes when I enter "LLUUUR". Why is it so? Using MinGW.

#include <cstdio>
#include <string>
#include <iostream>
int main() {
    std::string s;
    scanf("%s", &s);
    //std::cin >> s;
    char c = s[0];
}

推荐答案

scanf 对 std :: string 一无所知.如果要读入底层字符数组，则必须编写 scanf(％s"，s.data()); .但是请使用 std :: string :: resize(number)！

scanf knows nothing about std::string. If you want to read into the underlying character array you must write scanf("%s", s.data());. But do make sure that the string's underlying buffer is large enough by using std::string::resize(number)!

通常:请勿将 scanf 与 std :: string 一起使用.

Generally: don't use scanf with std::string.

如果要使用 scanf 和 std :: string

int main()
{
    char myText[64];
    scanf("%s", myText);

    std::string newString(myText);
    std::cout << newString << '\n';

    return 0;
}

读取后构造字符串.

现在直接在字符串上输入方式:

Now for the way directly on the string:

int main()
{
    std::string newString;
    newString.resize(100); // Or whatever size   
    scanf("%s", newString.data());

    std::cout << newString << '\n';

    return 0;
}

尽管这当然只会读到下一个空格.因此，如果您想阅读整行，则最好使用:

Although this will of course only read until the next space. So if you want to read a whole line, you would be better off with:

std::string s;
std::getline(std::cin, s);

这篇关于std :: cin和scanf()之间的区别应用于字符串的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！