C++11 为什么我的搜索功能不能按预期工作？我如何修复它？

我正在尝试创建一个比较搜索函数，它可以根据字符将两个字符串比较在一起。例如：

输入：“ca” 姓氏字段下的结构向量内容（排序向量）（索引/值）：0/“汽车”，1/“道路” 结果：“在索引0处找到名称-车辆”

我希望用户能够使用任意数量的字符。然后，程序应将提供的搜索条件与向量的内容进行比较，并返回任何匹配项的索引

到目前为止，我已经尝试实现这个算法，但没有成功，下面是我的代码。我对C++也是很新的。

// Function for searching through an array for a string value.
int searchArray(std::vector<playerdata> (&people), std::string name) {

    int loc = -1;
    int counter = 0;
    int index = 0;

    //when loc is no longer -1, that means the person has been found

    for (int i = 0; i < people.size(); i++)

        for(int k = 0; k < name.length(); k++) {

            std::cout << name[k-1] << std::endl;
            std::cout << people[i].lastname[k-1] << std::endl;
            std::cout << counter << std::endl;
            std::cout << "" << std::endl;

            if(name[k-1] == people[i].lastname[k-1]) {

                counter++;

            }

            if(counter == name.length()) {

                loc = i;
                break;

            }
        }

        //if (people[i].lastname.compare(name) == 0)

            //loc = i;

    return loc;

}

编辑：正如您可以从我的控制台输出中看到的那样，代码返回的是真正的比较，而它不应该这样做。一个例子是is（e==n）的最后一次比较。答案应该是错的，但它总是返回真的

使用注释中建议的代码后，我仍然无法使代码按预期工作，并出现以下错误：

    ||=== Build file: "no target" in "no project" (compiler: unknown) ===|
E:\Coding\Cplus_work\assignmentseven.cpp||In function 'int main()':|
E:\Coding\Cplus_work\assignmentseven.cpp|68|warning: NULL used in arithmetic [-Wpointer-arith]|
E:\Coding\Cplus_work\assignmentseven.cpp|158|warning: NULL used in arithmetic [-Wpointer-arith]|
c:\mingw\lib\gcc\mingw32\8.2.0\include\c++\bits\predefined_ops.h||In instantiation of 'bool __gnu_cxx::__ops::_Iter_pred<_Predicate>::operator()(_Iterator) [with _Iterator = __gnu_cxx::__normal_iterator<playerdata*, std::vector<playerdata> >; _Predicate = searchArray(std::vector<playerdata>&, std::__cxx11::string&)::<lambda(std::__cxx11::string&)>]':|
c:\mingw\lib\gcc\mingw32\8.2.0\include\c++\bits\stl_algo.h|120|required from '_RandomAccessIterator std::__find_if(_RandomAccessIterator, _RandomAccessIterator, _Predicate, std::random_access_iterator_tag) [with _RandomAccessIterator = __gnu_cxx::__normal_iterator<playerdata*, std::vector<playerdata> >; _Predicate = __gnu_cxx::__ops::_Iter_pred<searchArray(std::vector<playerdata>&, std::__cxx11::string&)::<lambda(std::__cxx11::string&)> >]'|
c:\mingw\lib\gcc\mingw32\8.2.0\include\c++\bits\stl_algo.h|161|required from '_Iterator std::__find_if(_Iterator, _Iterator, _Predicate) [with _Iterator = __gnu_cxx::__normal_iterator<playerdata*, std::vector<playerdata> >; _Predicate = __gnu_cxx::__ops::_Iter_pred<searchArray(std::vector<playerdata>&, std::__cxx11::string&)::<lambda(std::__cxx11::string&)> >]'|
c:\mingw\lib\gcc\mingw32\8.2.0\include\c++\bits\stl_algo.h|3930|required from '_IIter std::find_if(_IIter, _IIter, _Predicate) [with _IIter = __gnu_cxx::__normal_iterator<playerdata*, std::vector<playerdata> >; _Predicate = searchArray(std::vector<playerdata>&, std::__cxx11::string&)::<lambda(std::__cxx11::string&)>]'|
E:\Coding\Cplus_work\assignmentseven.cpp|35|required from here|
c:\mingw\lib\gcc\mingw32\8.2.0\include\c++\bits\predefined_ops.h|283|error: no match for call to '(searchArray(std::vector<playerdata>&, std::__cxx11::string&)::<lambda(std::__cxx11::string&)>) (playerdata&)'|
E:\Coding\Cplus_work\assignmentseven.cpp|33|note: candidate: 'searchArray(std::vector<playerdata>&, std::__cxx11::string&)::<lambda(std::__cxx11::string&)>'|
E:\Coding\Cplus_work\assignmentseven.cpp|33|note:   no known conversion for argument 1 from 'playerdata' to 'std::__cxx11::string&' {aka 'std::__cxx11::basic_string<char>&'}|
E:\Coding\Cplus_work\assignmentseven.cpp||In function 'bool sortArray(const playerdata&, const playerdata&)':|
E:\Coding\Cplus_work\assignmentseven.cpp|28|warning: control reaches end of non-void function [-Wreturn-type]|
||=== Build failed: 1 error(s), 8 warning(s) (0 minute(s), 0 second(s)) ===|

||===生成文件：“无项目”中的“无目标”（编译器：未知）===|
E:\Coding\Cplus_work\assignmentseven.cpp |在函数“int main（）”中：|
E:\Coding\Cplus|u work\assignmentseven.cpp | 68 |警告：算术中使用NULL[-Wpointer arith]|
E:\Coding\Cplus_work\assignmentseven.cpp | 158 |警告：算术中使用NULL[-Wpointer arith]|
c:\mingw\lib\gcc\mingw32\8.2.0\include\c++\bits\prefined_ops.h | | |在'bool_ugnu cxx:：：u ops:：_Iter_pred:：operator（）（_Iterator）[with u Iterator=u gnu cxx:：u normal Iterator；_谓词=searray（std:：vector&，std:uuux11:：string&]：]|
c:\mingw\lib\gcc\mingw32\8.2.0\include\c++\bits\stl|u algo.h | 120 |来自“_randomAccessIteratorstd:：u find_if（_RandomAccessIterator，_RandomAccessIterator，_Predicate，std:：random_accessIterator(标记）[带u RandomAccessIterator=u gnu cxx:：u normal iterator；u谓词=u gnu cxx:u ops:)|
c:\mingw\lib\gcc\mingw32\8.2.0\include\c++\bits\stl|u algo.h | 161 |来自“_iteratorstd:：u find_if（_Iterator，_Iterator，_Predicate）[带u Iterator=u gnu cxx:：u normal Iterator；u predicator=u gnu cxx:u-gnu-cxx:u-gnu-cxx:u-Iter:：u-ops:u-pred:u-Iter:|
c:\mingw\lib\gcc\mingw32\8.2.0\include\c++\bits\stl_algo.h | 3930 |来自“_iiterstd:：find_if（_IIter，_IIter，_IIter，_Predicate）[with IIter=u gnu cxx:：u normal iterator；_Predicate=searray（std:：vector&，std:uuuuuucx11:：string&）]：]|
E:\Coding\Cplus|u work\assignmentseven.cpp | 35 |此处必填|
c:\mingw\lib\gcc\mingw32\8.2.0\include\c++\bits\predefined_ops.h | 283 |错误：调用（searchArray（std:：vector&，std:uucxx11:：string&）：（playerdata&）不匹配|
E:\Coding\Cplus_work\assignmentseven.cpp | 33 |注：候选者：'searchArray（std:：vector&，std:：uu cxx11:：string&）：'|
E:\Coding\Cplus_work\assignmentseven.cpp | 33 |注：参数1从'playerdata'到'std:：uuuuucx11:：string&'{aka'std:：uuucx11:：basic_string&'）没有已知的转换|
E:\Coding\Cplus_work\assignmentseven.cpp |在函数“bool sortArray（const playerdata&，const playerdata&）”中：|
E:\Coding\Cplus|u work\assignmentseven.cpp | 28 |警告：控件到达非无效函数的末尾[-Wreturn type]|
||==生成失败：1个错误，8个警告（0分钟，0秒））===|

我使用的确切代码是：

// Function for searching through an array for a string value.
int searchArray(std::vector<playerdata> (&people), std::string (&name))
{
    auto it = std::find_if(people.begin(), people.end(), [&name](std::string& person){
        return person.find(name) != std::string::npos;
    });

    if(it != people.end()) {

        return std::distance(people.begin(), it);

    } else {

        return -1;

    }
}

//用于在数组中搜索字符串值的函数。
int searchArray（std:：vector（&people），std:：string（&name））
{
auto it=std:：find_if（people.begin（）、people.end（）、[&name]（std:：string&person）{
返回person.find（name）！=std:：string:：npos；
});
if（it！=people.end（））{
return std:：distance（people.begin（），it）；
}否则{
返回-1；
}
}

主要问题可能是当

k=0

时，您试图访问

name[k-1]

和

lastname[k-1]

，这会导致UB

在继续你的工作之前，开始学习。考虑到这一点，仅使用

find_if

和

std:：string:：find

:

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

struct playerdata
{
    std::string lastname;

    playerdata(std::string lastname) :
        lastname(std::move(lastname))
    {
    }
};

int searchArray(std::vector<playerdata>& people, const std::string& name) 
{
    auto it = std::find_if(people.cbegin(), people.cend(), [&name](const playerdata& player){
        return player.lastname.find(name) != std::string::npos;
    });

    if(it != people.end())
        return std::distance(people.cbegin(), it);
    else 
        return -1;
}

---

#include可能主要问题是当
k=0
时，您试图访问
name[k-1]
和
lastname[k-1]
，这会导致UB

在继续你的工作之前，开始学习。考虑到这一点，仅使用
find_if
和
std:：string:：find
:

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

struct playerdata
{
    std::string lastname;

    playerdata(std::string lastname) :
        lastname(std::move(lastname))
    {
    }
};

int searchArray(std::vector<playerdata>& people, const std::string& name) 
{
    auto it = std::find_if(people.cbegin(), people.cend(), [&name](const playerdata& player){
        return player.lastname.find(name) != std::string::npos;
    });

    if(it != people.end())
        return std::distance(people.cbegin(), it);
    else 
        return -1;
}

#包括
首先，你的解决方法是正确的，但需要一些技巧
改进
我假设你不想用正则表达式或模板C++函数来解决它。
哪种方式更好
您可能对中断声明有误解，这会影响
只有它被写入的循环
我已经在评论中解释了缺失点和需要改进的地方

线条
因为你没有详细说明所有的细节，我不得不假设它们
`

SearchArray（std:：vector&people，const std:：string&keyWord）
{
int loc=-1；
//使用更好的变量名来解释其用途，而不是'i'`
//所以你和其他像我们这样的人可以更快地理解它的意思
对于（int-vectorIndex=0；vectorIndexpeople[vectorIndex].lastname.length（））
{
继续；
}
int计数器=0；
int charIndexKeyWord=0；
//使用更好的变量名来解释其用途，而不是'k'`
对于（int charIndexIarget=0；charIndexIarget首先，你的解决方法是正确的，但需要一些技巧
改进
我假设你不想用正则表达式来解决它
SearchArray(std::vector<playerdata>& people, const std::string& keyWord) 
{

  int loc = -1;

  // Use a better variable name to explain its purpose instead of `i`
  // so you and other people like us can understand its meaning much faster
  for (int vectorIndex = 0; vectorIndex < people.size(); vectorIndex++)
  {
    // if length of the name is bigger than a lastname it can`t be a match so just continue
    if (keyWord.length() > people[vectorIndex].lastname.length())
    {
        continue;
    }

    int counter = 0;
    int charIndexKeyWord = 0;
    // Use a better variable name to explain its purpose instead of `k`
    for (int charIndexIarget = 0; charIndexIarget < people[vectorIndex].lastname.length(); charIndexIarget++)
    {           
        // Your for loop starts from 0 but you're trying to use [k-1] in your code
        // you shouldn't do that, because in the first iteration of the loop it will indicate -1 [k-1]
        // but it starts with 0, 

        //std::cout << keyWord[charIndexKeyWord] << std::endl;
        //std::cout << people[vectorIndex].lastname[charIndexIarget] << std::endl;
        //std::cout << counter << std::endl;
        //std::cout << "" << std::endl;

        // This is part of your code which needs improvment
        if (keyWord[charIndexKeyWord] == people[vectorIndex].lastname[charIndexIarget]) 
        {
            counter++; 
            charIndexKeyWord++;
        }
        else
        {
            // If you keep your code as it is, it will may also consider matches like susnhine `sun` because
            // so you need to make some improvements to get rid of it.
            // if you have already founded a match but next word is not a match then you need to start looking from  the beginning
            if (counter != 0)
            {
                counter = 0;
                charIndexKeyWord = 0;                   
            }               
        }

        if (counter == keyWord.length())
        {

            loc = vectorIndex;
        }
    }

    if (loc != -1)
    {
        break;
    }

}

return loc;