Question

我必须编写一个程序，允许用户输入最多20个名称 最多40个字符。

当我编写代码而不试图以任何方式限制字符串长度时，它可以工作。但是当我尝试使用if / else语句限制字符串长度时，它不起作用。我对C ++很陌生，所以它真的是在黑暗中拍摄的。我做错了什么？

#include <iostream>
#include <string>
#include <set>
#include <algorithm>

using namespace std;

void print(const string& name) {
    cout << name << endl;
}

int main() {
    set<string> ListOfNames;
    cout << "Please enter up to 20 names of up to 40 characters each below:     " << endl;
for (int i = 1; i <= 20; ++i) {
    string name;
    cout << i << ". ";
    getline(cin, name);
    if (name.size() >= 40) {
        ListOfNames.insert(name);
    }
    else break;
    cerr << "You entered more than 40 characters. Please try again.";
}

for_each(ListOfNames.begin(), ListOfNames.end(), &print);
return 0;

}

输出：

1. (user inputs name here)
press any key to continue...

已编辑的代码：

#include <iostream>
#include <string>
#include <set>
#include <algorithm>

using namespace std;

void print(const string& name) {
    cout << name << endl;
}

int main() {
    set<string> ListOfNames;
    cout << "Please enter up to 20 names of up to 40 characters each below:         " << endl;
for (int i = 1; i <= 20; ++i) {
    string name;
    cout << i << ". ";
    getline(cin, name);
    if (name.size() <= 40) {
        ListOfNames.insert(name);
    }
    else
    {
        cerr << "You entered more than 40 characters. Please try again.";
        break;
    }

    for_each(ListOfNames.begin(), ListOfNames.end(), &print);
    return 0;
    }
}

Answer 1

如果字符串大于40且不小于40

，您似乎只说运行代码

Answer 2

编写一个单独的函数来获取并验证输入。在该函数中，检查输入是否少于40个字符，如果不是，则拒绝接受：

std::string get_limited_string(std::string prompt, int max = 40) {
    std::string input;
    do {
        std::cout << prompt;
        std::getline(std::cin, input);
    } while (input.size() >= max);
    return input;
}

Answer 3

inside如果将条件更改为name.size（）＆gt; = 40

并且in cr在crr之后中断并且两个语句都应该在{}

之内

if (name.size() <= 40) {
    ListOfNames.insert(name);
}
else
{
    cerr << "You entered more than 40 characters. Please try again.";
    break;
}

限制字符串长度？

3 个答案: