CSV数据提取后两行合并至同一单元格问题求助

Hey, let's figure out what's going wrong here and fix it step by step!

The Root Causes of Your Issue #

From your description and code, there are a few key issues leading to the merged cells in your output CSV:

• Wrong delimiter for parsing: Your input CSV uses semicolons (;) as separators, but your code is splitting lines using commas (,) with getline(lineStream,cell,','). This means each entire line is being treated as a single cell, which throws off the column structure entirely.
• Unescaped commas in output: You're replacing dots (.) with commas in cell content, but CSV rules require that any cell containing commas (or quotes/newlines) be wrapped in double quotes. Without this, tools like Excel will interpret those commas as column separators, leading to messed-up rows and merged cells.
• Inefficient column filtering: Your inner for loop runs 5 times for every cell—this isn't the direct cause of the merge issue, but it's unnecessary and can be optimized.

Fixed Code #

Here's the revised code that addresses all these problems, plus a bonus implementation of your missing row-filtering logic:

#include <iostream>
#include <sstream>
#include <fstream>
#include <string>
#include <algorithm>
#include <unordered_set>
using namespace std;

int main(){
    // Names of entries to keep (for row filtering)
    unordered_set<string> rows2keep = {"Name1","Name2"};
    // Column indices to keep (1-based matching your input structure)
    unordered_set<int> cols2keep = {1,2,3,4,5};
    
    ifstream data("Nameoffile.csv");
    if (!data.is_open()) {
        cerr << "Oops! Failed to open the input file." << endl;
        return 1;
    }
    
    ofstream outdata("sorting.csv");
    if (!outdata.is_open()) {
        cerr << "Oops! Failed to create the output file." << endl;
        data.close();
        return 1;
    }
    
    string line;
    int row_num = 0;
    
    while(getline(data, line)){
        row_num++;
        stringstream lineStream(line);
        string cell;
        int col_num = 0;
        bool first_cell = true;
        string current_name;

        // First, grab the Name value for row filtering (assuming Name is column 2)
        string temp_line = line;
        stringstream temp_stream(temp_line);
        int temp_col = 0;
        while(getline(temp_stream, cell, ';') && temp_col < 2){
            temp_col++;
            if (temp_col == 2) current_name = cell;
        }

        // Skip non-header rows that don't match our target names
        if (row_num > 1 && rows2keep.find(current_name) == rows2keep.end()) {
            continue;
        }

        // Process each cell in the row
        stringstream lineStreamProcess(line);
        while(getline(lineStreamProcess, cell, ';')){ // Use semicolon to split input cells
            col_num++;
            if (cols2keep.count(col_num)){
                // Replace dots with commas as required
                replace(cell.begin(), cell.end(), '.', ',');
                
                // Wrap cell in quotes if it contains commas/quotes/newlines (CSV standard)
                if (cell.find(',') != string::npos || cell.find('"') != string::npos || cell.find('\n') != string::npos) {
                    // Escape existing quotes by doubling them
                    size_t pos = 0;
                    while ((pos = cell.find('"', pos)) != string::npos) {
                        cell.replace(pos, 1, "\"\"");
                        pos += 2;
                    }
                    cell = "\"" + cell + "\"";
                }
                
                // Add separator before cell (avoid extra semicolon at row start)
                if (!first_cell) {
                    outdata << ";";
                    cout << ";";
                } else {
                    first_cell = false;
                }
                
                outdata << cell;
                cout << cell;
            }
        }
        // Add newline after each valid row
        outdata << "\n";
        cout << "\n";
    }
    
    data.close();
    outdata.close();
    return 0;
}

Key Fixes Explained #

1. Correct input delimiter: Changed getline(lineStream, cell, ',') to getline(lineStream, cell, ';') to match your input CSV's semicolon separators. This ensures each cell is parsed correctly.
2. Proper CSV escaping: Added logic to wrap cells containing commas (or quotes/newlines) in double quotes, and escape any existing quotes by doubling them. This ensures tools like Excel read the CSV without mangling rows.
3. Optimized filtering: Switched to unordered_set for columns/rows to keep—checking if a column/row should be preserved is now O(1) instead of looping through arrays every time.
4. Added error checking: The code now verifies if files open successfully, so you'll get a clear message if something's wrong with file paths.
5. Row filtering implemented: Added logic to skip rows that don't match your target names, while keeping the header row intact.

内容的提问来源于stack exchange，提问作者Vincent-Olivier Faullem