Question

我目前正在学习Bjarne Stroustrup的初学者书，我在第4章练习19，所以请不要使用高于我的水平的代码。我不明白为什么if(name == names[i])不起作用。所以这是我目前的代码：

/*
Vladar Akos
Chapter 4 Exercise 19.
2018.03.26

Write a program where you first enter a set of name-and-value pairs, such as Joe 17 and Barbara 22. For each pair, add
the name to a vector called names and the number to a vector called scores (in corresponding positions, so that if
names[7]=="Joe" then scores[7]==17). Terminate input with NoName 0. Check that each name is unique and
terminate with an error message if a name is entered twice. Write out all the (name,score) pairs, one per line.
*/

#include <iostream>
#include <string>
#include <cmath>
#include <vector>
#include <algorithm>

int main()
{
    std::vector<int>scores;
    std::vector<std::string>names;
    std::string name = " ";
    int score = 0;
    bool first = true;
    std::cout << "Please write in a name and a score (terminate input with 'NoName') : \n";
    while ((std::cin >> name >> score) && (name != "NoName") && (score != 0))
    {
        if (first == true)
        {
            scores.push_back(score);
            names.push_back(name);
        }
        else
        {
            for (int i = 0; i < names.size(); i++)
            {
                if (name == names[i]) std::cout << "Same name as before!\n";
                else
                {
                    scores.push_back(score);
                    names.push_back(name);
                }
            }
            first = false;
        }
        std::cout << "Please write more names and scores: ";        
    }
    for (int i = 0; i < names.size(); i++)
    {
        std::cout << names[i] << '\t' << scores[i] << "\n";
    }
}

如果两次输入名称，我该怎么做才能使程序抛出错误信息？ P.S。：这是我的第一篇文章，如果出现问题就很抱歉

编辑：谢谢你的帮助！这对我来说是一个愚蠢的错误。 Swapnil 的答案解决了我的问题，但每个人都帮了很多忙。

Answer 1

您应该在处理第一个输入后立即first false，否则它将永远不会输入其他内容。将first = false置于else语句之外。另一个问题是，一旦你发现有重复你应该停止搜索，也就是打破循环。：

while ((std::cin >> name >> score) && (name != "NoName") && (score != 0)) {
    if (first == true) {
        scores.push_back(score);
        names.push_back(name);
    }
    else {
        for (int i = 0; i < names.size(); i++) {
            if (name == names[i]) {
                std::cout << "Same name as before!\n";
            }
            else {
                scores.push_back(score);
                names.push_back(name);
                break;
            }
        }
    }
    first = false;
    std::cout << "Please write more names and scores: ";        
}

Answer 2

#include <iostream>
#include <string>
#include <cmath>
#include <vector>
#include <algorithm>

int main()
{
    std::vector<int>scores;
    std::vector<std::string>names;
    std::string name = " ";
    int score = 0;
    bool first = true;
    std::cout << "Please write in a name and a score (terminate input with 'NoName') : \n";
    while ((std::cin >> name >> score) && (name != "NoName") && (score != 0))
    {
        if (first == true)
        {
            scores.push_back(score);
            names.push_back(name);
        }
        else
        {
            bool duplicate = false;
            for (int i = 0; i < names.size(); i++)
            {
                if (name == names[i])
                    duplicate = true;
            }

            if(duplicate)
            {
                std::cout << "Same name as before!\n";
            }
            else
            {
                scores.push_back(score);
                names.push_back(name);
            }
        }
        first = false;
        std::cout << "Please write more names and scores: ";
    }
    for (int i = 0; i < names.size(); i++)
    {
        std::cout << names[i] << '\t' << scores[i] << "\n";
    }
}

将false放在else之外，然后添加bool标志，我们在插入vector之前检查它们是否重复

连同输出

Please write in a name and a score (terminate input with 'NoName') :
JON
20
Please write more names and scores: SAM
50
Please write more names and scores: PETER
50
Please write more names and scores: PETER
70
Same name as before!
Please write more names and scores: SAM
89
Same name as before!
Please write more names and scores: NoName
0
JON     20
SAM     50
PETER   50
Press <RETURN> to close this window...

当名称输入相同时，如何使我的代码给出错误消息？

2 个答案: