Question

How to sum 2D array (matrix) cols in C++

Answer 1

#include <iostream>

using std::cout;
using std::endl;

void sum_matrix_cols(int matrix[][5], int cols_sum[3], int rows, int cols)
{
	for (int j = 0; j < cols; j++) {
		for (int i = 0; i < rows; i++)
			cols_sum[j] += matrix[i][j];
	}
}

int main()
{
	int matrix[3][5] = { { 1, 2, 3, 4, 5 },
	                     { 1, 2, 3, 4, 5 },
	                     { 1, 2, 3, 4, 5 } };

	int cols_sum[5] = { 0 };
	int rows = sizeof matrix / sizeof matrix[0];
	int cols = sizeof matrix[0] / sizeof(int);

	sum_matrix_cols(matrix, cols_sum, rows, cols);

	for (int i = 0; i < 5; i++)
		cout << cols_sum[i] << endl;

	return 0;
}



/*
run:

3
6
9
12
15

*/

 

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