为散列程序读取带有分隔符和空行的文件

Reading in a file with delimiter and blank lines for hashing program

本文关键字：文件 分隔符 程序 读取      更新时间：2023-10-16

如何从文件中读取行并将该行的特定段分配给结构体中的信息?我如何在空白行处停止，然后继续，直到到达文件末尾?

背景:我正在构建一个程序，它将接收一个输入文件，读入信息，并使用双哈希法将该信息放入哈希表的正确索引中。

假设我有一个结构体:

struct Data
{
    string city;
    string state;
    string zipCode;
};

但是文件中的行格式如下:

20
85086,Phoenix,Arizona
56065,Minneapolis,Minnesota
85281
56065
我似乎弄不明白这个。我真的很难读懂这份文件。第一行基本上是要构造的哈希表的大小。下一个空行应该被忽略。接下来的两行是应该进入结构体并被散列到散列表中的信息。那么另一个空行应该被忽略。最后，最后两行是需要匹配的输入，以查看它们是否存在于哈希表中。所以在这种情况下，没有找到85281。而56065被找到。

这是我所拥有的，它似乎没有做我想要它做的事情:

int main(int argc, char *argv[])
{
string str;
//first line of file is size of hashtable
getline(cin, str);
stringstream ss(str);
int hashSize;
ss >> hashSize;
//construct hash table
Location *hashTable = new Location[hashSize];
//skip next line
getline(cin, str);
string blank = " ";
while(getline(cin, str))
{

    {
        //next lines are data
        Location locate;
        string line;
        getline(cin, line);
        istringstream is(line);
        getline(is, locate.zipCode, ',');
        getline(is, locate.city, ',');
        getline(is, locate.state, ',');
    insertElementIntoHash(hashTable, locate, hashSize);
    }
}
    dispHashTable(hashTable, hashSize);
//read third set of lines that check if the zipCodes are in the hashtable or not
while(getline(cin, str))
{
    //stop reading at a blank line or in this case, end of file

    stringstream is(str);
    string searchZipCode;
    is >> searchZipCode;
    searchElementInHash(hashTable, hashSize, searchZipCode);
}

//delete hash table after use
delete []hashTable;
return 0;
}

您可以这样读取输入:

#include <iostream>
#include <sstream>
#include <vector>
struct Location
{
    std::string city;
    std::string state;
    std::string zipCode;
};
int main(int argc, char *argv[]) {
    std::istringstream input(
        "2n"
        "n"
        "85086,Phoenix,Arizonan"
        "56065,Minneapolis,Minnesotan"
        "n"
        "85281n"
        "56065n"
    );
    // Make the size unsigned, to avoid signed/unsigned compare warnings.
    unsigned hashSize;
    std::string line;
    getline(input, line);
    std::istringstream hash_line(line);
    // Ignore white space.
    if( ! (hash_line >> hashSize >> std::ws && hash_line.eof())) {
        std::cerr << "Error: Invalid file format [1].n" << line << 'n';
        return -1;
    }
    else {
        getline(input, line);
        std::istringstream first_blank_line(line);
        // Ignore white space.
        first_blank_line >> std::ws;
        if( ! first_blank_line.eof()) {
            // Missing blank line.
            std::cerr << "Error: Invalid file format [2].n" << line << 'n';
            return -2;
        }
        else {
            // Have a local variable (No need to allocate it)
            // (Is it a hash table !???)
            std::vector<Location> hashTable;
            hashTable.reserve(hashSize);
            while(hashTable.size() < hashSize && getline(input, line)) {
                std::istringstream data_line(line);
                Location locate;
                getline(data_line, locate.zipCode, ',');
                getline(data_line, locate.city, ',');
                getline(data_line, locate.state); // Note: No comma here.
                if(data_line && data_line.eof()) {
                    // Note: The fields may have leading and/or trailing white space.
                    std::cout
                        << "Insert the location into the hash table.n"
                        << locate.zipCode << 'n'
                        << locate.city << 'n'
                        << locate.state << 'n';
                    hashTable.push_back(locate);
                }
                else {
                    std::cerr << "Error: Invalid file format [3].n" << line << 'n';
                    return -3;
                }
            }
            if(hashTable.size() != hashSize) {
                std::cerr << "Error: Invalid file format [4].n";
                return -4;
            }
            else {
                getline(input, line);
                std::istringstream second_blank_line(line);
                // Ignore white space.
                second_blank_line >> std::ws;
                if( ! second_blank_line.eof()) {
                    // Missing blank line.
                    std::cerr << "Error: Invalid file format [5].n";
                    return -5;
                }
                else {
                    std::string searchZipCode;
                    while(input >> searchZipCode) {
                        // Search element in the hash table
                    }
                }
            }
        }
    }
    return 0;
}

以下修改应该可以工作:

//skip next line
getline(cin, str);
string blank = " ";
string line;
while(getline(cin, line) && (line != ""))
{

    {
        //next lines are data
        Location locate;
        istringstream is(line);
        getline(is, locate.zipCode, ',');
        getline(is, locate.city, ',');
        getline(is, locate.state, ',');
    insertElementIntoHash(hashTable, locate, hashSize);
    }
}
相关文章：