将矩阵加载到2D矢量C ++中

Question

I am new to using vectors in C++, my goal is to read a matrix from the text file and store them into a 2D vector, My code is as follows :

#include <fstream>
#include <iostream>
#include <sstream>
#include <string>
#include <vector>
int main()
{
    std::ifstream in("input.txt");
    std::vector<std::vector<int> > v;

    if (in) {
        std::string line;

        while (std::getline(in, line)) {
            v.push_back(std::vector<int>());

            // Break down the row into column values
            std::stringstream split(line);
            int value;

            while (split >> value)
                v.back().push_back(value);
        }
    }

    for (int i = 0; i < v.size(); i++) {
        for (int j = 0; j < v[i].size(); j++)
            std::cout << v[i][j] << ' ';

        std::cout << '\n';
    }
}

now for an input of say

10101010
01010101
10101011
01011010

I get an output of

10101010
1010101
10101011
1011010

ie everytime a 0 is encountered in the beginning of a line it is omitted. I believe the problem is in the statement while(split>>value), but I dont know how to code it in a better way.

Answer 1

Replace

while (split >> value)
    v.back().push_back(value);

with

for(int x=0; x<line.size(); x++){
    v.back().push_back((int)line[x] - (int)'0'));
}

and remove your string stream completely.

Answer 2

It seems as if you actually want to store bits, but somehow struggled with parsing a line containing, for example, 10101010 into a series of bits. If you know the maximum number of bits per line, you could use bitset<N> , which provide an easy to use overload for operator >> that can directly read in something like 10101010 . Hope it helps.

int main()
{
    std::ifstream in("input.txt");
    std::vector<std::bitset<8> >v;

    if (in) {
        std::bitset<8> bits;
        while (in >> bits) {
            v.push_back(bits);
        }
    }

    for (int i = 0; i < v.size(); i++) {
        for (int j = 0; j < v[i].size(); j++)
            std::cout << v[i][j] << ' ';

        std::cout << '\n';
    }
}