将STL映射打印为表格

Question

I have a map defined as map<string, vector<double> > .

How do I print this as a table. I want the key of the map to be the title row of the table and the each column of the table will be the vector

Say my initial map was

hash = {
  "a": [1, 2, 3],
  "b": [1, 2, 3]
}

I want this printed as

a b
1 1
2 2
3 3

Answer 1

Flexible for arbitrary columns and variant length

void print(const map<string, vector<double>> &m)
{
    size_t rows = 0;
    for (auto const &i : m)
    {
        cout << i.first << ' ';
        if (i.second.size() > rows)
            rows = i.second.size();
    }
    cout << endl;
    for (size_t r = 0; r < rows; ++r)
    {
        for (auto const &i : m)
            if (r < i.second.size())
                cout << i.second[r] << " ";
            else
                cout << "  ";
        cout << endl;
    }
}
int main()
{ 
    map<string, vector<double> > m = {
        { "a", { 1, 2, 3}},
        { "b", { 1, 2, 3, 4}},
        { "c", { 1, 2}},
        { "d", { 1}},
        { "e", { 1, 2, 3, 4, 5, 6, 7}}
    };
    print(m);
}

Output

 a b c d e
 1 1 1 1 1
 2 2 2   2
 3 3     3
   4     4
         5
         6
         7

Live source code.

Answer 2

Here is a possible implementation using C++11 (here I expect all vectors to have the same size ):

#include <map>
#include <string>
#include <vector>
#include <iostream>

void print(std::map<std::string, std::vector<double>> const& m)
{
    // Do nothing for an empty table...
    if (m.begin() == m.end()) { return; }

    for (size_t i = 0; i <= m.begin()->second.size(); i++)
    {
        for (auto const& p : m)
        {
            if (i == 0) { std::cout << p.first << " "; }
            else { std::cout << p.second[i - 1] << " "; }
        }

        std::cout << std::endl;
    }
}

int main()
{
    std::map<std::string, std::vector<double>> m = {
        { "a", { 1, 2, 3, 0 } },
        { "b", { 2, 4, 6, 1 } },
        { "c", { 9, 2, 3, 2 } }
    };

    print(m);
}

And here is a live example .

Answer 3

This works with vectors with different lengths:

#include <iostream>
#include <map>
#include <vector>
#include <string>

using namespace std;

int main()
{

    map<string,vector<double> > hashes;
    double arr[]={1,2,3};
    double arr2[]={1,2,3,4};
    hashes.insert(pair<string,vector<double> >("a",vector<double>(arr,arr+sizeof(arr)/sizeof(double))));
    hashes.insert(pair<string,vector<double> >("b",vector<double>(arr,arr+sizeof(arr)/sizeof(double))));
    hashes.insert(pair<string,vector<double> >("c",vector<double>(arr2,arr2+sizeof(arr2)/sizeof(double))));

    for(auto i: hashes)
    {
        cout<< i.first << ' ';
    }
    cout << endl;
    int max_len=0;
    for(auto i: hashes)
    {
    if(i.second.size()>max_len) max_len=i.second.size();
    }
    for(int h=0; h<max_len; h++)
    {

    for(auto i: hashes)
    {
        if(h>=i.second.size()) cout << "  ";
        else cout << i.second[h] << " ";
    }
    cout << endl;
}
return 0;
}

Output:

a b c
1 1 1
2 2 2
3 3 3
    4

Answer 4

#include <iostream>
#include <map>
#include <string>
#include <vector>
using namespace std;

int main()
{
    map<string, vector<double> > m;
    vector<double> a, b, c;
    for (int i = 0; i < 4; ++i) a.push_back(i);
    for (int i = 0; i < 6; ++i) b.push_back(i);
    for (int i = 0; i < 7; ++i) c.push_back(i);
    m["a"] = a;
    m["b"] = b;
    m["c"] = c;

    int n = max(max(a.size(), b.size()), c.size());
    for (map<string, vector<double> >::iterator i = m.begin(); i != m.end(); ++i)
        cout << i->first << ',';
    cout << endl;

    for (int i = 0; i < n; ++i) {
       for (map<string, vector<double> >::iterator it = m.begin(); it != m.end(); ++it)
           cout << (i < it->second.size() ? it->second[i] : 0) << ',';
       cout << endl;
    }
}

I believe there are better ways to do the iteration and to deal with the trailing , .

Answer 5

This solution will work for an arbitrary number of columns, each with an arbitrary number of rows.

And column names also with an arbitrary length.

#include <map>
#include <string>
#include <vector>
#include <iostream>

void print(std::map<std::string, std::vector<double>> const& m)
{
    std::vector<size_t> columnWidths;
    std::vector< std::vector<std::string>> columns;
    size_t totalRows = 0;

    // Store all table elements, and the required width of each column
    for ( auto a : m )
    {
       std::vector<std::string> column;
       size_t width = a.first.length();
       column.push_back( a.first );
       size_t rows = 1;

       for ( auto v : a.second )
       {
          ++rows;
          std::string entry = std::to_string(v);
          width = std::max( width, entry.length() );
          column.push_back( entry );
       }
       columnWidths.push_back( width );
       columns.push_back( column );
       totalRows = std::max( totalRows, rows );
    }

    // Print all table elements
    for ( size_t row = 0; row != totalRows; ++row )
    {
        for ( size_t col = 0; col != columns.size(); ++col )
        {
            std::string entry;
            if ( columns[col].size() > row )
            {
                entry = columns[col][row];
            }
            entry.resize( columnWidths[col], ' ' );
            std::cout << entry << ' ';
        }
        std::cout << '\n';
    }
}

int main()
{
    std::map<std::string, std::vector<double>> m =
    {
        { "a", { 1, 2, 3} },
        { "a really really long string", { 1, 2, 3} },
        { "b", { 1, 2, 3, 4, 5 } }
    };

    print(m);
}