Question

How to find the sum of boundaries and diagonals of a matrix in C++

Answer 1

#include <iostream>

#define COLS 5
 
int sumDiagonalsAndBoundaries(int matrix[][COLS], int rows, int cols) {
    int sumBoundaries = 0, sumDiagonals = 0;
 
    for (int i = 0; i < rows; i++) {
        for (int j = 0; j < COLS; j++) {
            if (i == j) {
                sumDiagonals += matrix[i][j];
            }
            if ((i + j) == rows - 1) {
                sumDiagonals += matrix[i][j];
            }
            if (i == 0 || j == 0 || i == rows - 1 || j == cols - 1) {
                sumBoundaries += matrix[i][j];
            }
        }
    }
 
    std::cout << "sumBoundaries = " << sumBoundaries << "\n";
    std::cout << "sumDiagonals = " << sumDiagonals << "\n";
 
    return sumBoundaries + sumDiagonals;
}
 
 
int main()
{
    int matrix[][COLS] = { { 1,   2,   3,   4,  0 },
                           { 5,   6, 100,   8,  1 },
                           { 2, 100,   8, 100,  3 },
                           { 1,   7, 100,   9,  6 },
                           { 9,  10,  11,  12, 13 } };
 
    // sumBoundaries = (1 + 2 + 3 + 4 + 0) = 10 + (1 + 3 + 6 + 13)  = 23 + 
    //                 (12 + 11 + 10 + 9) = 42 + (1 + 2 + 5) = 9 : 10 + 23 + 42 + 8 = 83
     
    // sumDiagonals = (1 + 6 + 8 + 9 + 13) = 37 + (0 + 8 + 8 + 7 + 9) = 32 : 37 + 32 = 69
 
    // 83 + 69 = 152
 
    int rows = sizeof matrix / sizeof matrix[0];
    int cols = sizeof matrix[0] / sizeof(int);
 
    std::cout << sumDiagonalsAndBoundaries(matrix, rows, cols);
}
 
 
 
 
/*
run:
 
sumBoundaries = 83
sumDiagonals = 69
152
 
*/

 

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Answer 2

#include <iostream>

#define COLS 5

int sumDiagonalsAndBoundaries(int matrix[][COLS], int rows, int cols) {
    int sumBoundaries = 0, sumDiagonalLeft = 0, sumDiagonalRigth = 0;
 
    for (int i = 0; i < rows; i++) {
        sumDiagonalLeft += matrix[i][i];
        sumDiagonalRigth += matrix[i][cols - i - 1];
        for (int j = 0; j < COLS; j++) {
            if (i == 0 || j == 0 || i == rows - 1 || j == cols - 1) {
                sumBoundaries += matrix[i][j];
            }
        }
    }
 
    std::cout << "sumBoundaries = " << sumBoundaries << "\n";
    std::cout <<"sumDiagonalLeft = " << sumDiagonalLeft << "\n";
    std::cout << "sumDiagonalRigth = " << sumDiagonalRigth << "\n";
 
    return sumBoundaries + sumDiagonalLeft + sumDiagonalRigth;
}
 
 
int main()
{
    int matrix[][COLS] = { { 1,   2,   3,   4,  0 },
                           { 5,   6, 100,   8,  1 },
                           { 2, 100,   8, 100,  3 },
                           { 1,   7, 100,   9,  6 },
                           { 9,  10,  11,  12, 13 } };
 
    // sumBoundaries = (1 + 2 + 3 + 4 + 0) = 10 + (1 + 3 + 6 + 13)  = 23 + 
    //                 (12 + 11 + 10 + 9) = 42 + (1 + 2 + 5) = 9 : 10 + 23 + 42 + 8 = 83
 
    // sumDiagonalLeft = (1 + 6 + 8 + 9 + 13) = 37 
    // sumDiagonalRigth = (0 + 8 + 8 + 7 + 9) = 32
 
    // 83 + 37 + 32 = 152
 
    int rows = sizeof matrix / sizeof matrix[0];
    int cols = sizeof matrix[0] / sizeof(int);
 
    std::cout << sumDiagonalsAndBoundaries(matrix, rows, cols);
}
 
 
 
 
/*
run:
 
sumBoundaries = 83
sumDiagonalLeft =  37
sumDiagonalRigth = 32
152
 
*/

 

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