Question

How to get 2D vector rows and columns (cols) in C++

Answer 1

#include <iostream>
#include <vector>

int main() {
    std::vector<std::vector<int>> vec2d {
        { 1, 4, 8, 9 },
        { 0, 7, 1, 3, 40 },
        { 5, 2, 13, 28, 50, 60, 99 }
    };

    int rows = vec2d.size();
    std::cout << "rows: " << rows << "\n";
    
    for (int i = 0; i < rows; i++) {
        for (int j = 0; j < vec2d[i].size(); j++) {
            std::cout << "row: " << i << " cols: " << vec2d[i].size() << "\n";
            break;
        }    
    }
}





/*
run:

rows: 3
row: 0 cols: 4
row: 1 cols: 5
row: 2 cols: 7

*/

 

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Answer 2

#include <iostream>
#include <vector>

int main() {
    std::vector<std::vector<int>> vec2d {
        { 1, 4, 8, 9 },
        { 0, 7, 1, 3 },
        { 5, 2, 13, 28 }
    };

    int rows = vec2d.size();
    std::cout << "rows: " << rows << "\n";
    
    int cols = vec2d[0].size();
    std::cout << "cols: " << cols << "\n";
}





/*
run:

rows: 3
cols: 4

*/

 

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