sumOfDiagonals.js (***Coding test***)

 /**Sum of Diagonals

Description

Given a square matrix, print the sum of all the numbers on both the diagonals.

Input format

First line contains a positive integer n, denoting the number of rows and columns It is

followed by n lines. Each line contains space separated integers denoting elements of that

row.

Output format

One line containing the sum of all the numbers on both the diagonals.

Sample input

3

1 2 3

4 5 6

7 8 9

Sample output

30

Explanation

First line is 3, i.e. 3 rows and 3 columns. We can see that there are 2 diagonals [1,5,9] and

[3,5,7]. When we add all the numbers in both the diagonals, it comes up to 15 + 15 which i

s 30 which is our output

*/

let fs = require("fs");

let data = fs.readFileSync(0, 'utf-8');

let idx = 0;

data = data.split('\n');

function readLine() {

idx++;

return data[idx - 1].trim();

}

/////////////////////////////////////////////////////////////////////////////////////////////////////////////

// This part is only for taking Inputs

const rowsAndcoloumns = parseInt(readLine()); // 3 is the no. of rows and coloumns

let arr = []; // we will push all the elements in this array

for (let i = 0; i < rowsAndcoloumns; i++) {

let elements = readLine().split(" ");

// console.log(elements); // [ '1', '2', '3' ]

// [ '4', '5', '6' ]

// [ '7', '8', '9' ] , all green color elements.

for (let j = 0; j < rowsAndcoloumns; j++) {

elements[j] = parseInt(elements[j])

}

// console.log(elements); // [ 1, 2, 3 ]

// [ 4, 5, 6 ]

// [ 7, 8, 9 ] , all yellow color elements.

arr.push(elements)

}

// console.log(arr); // [ [ 1, 2, 3 ], [ 4, 5, 6 ], [ 7, 8, 9 ] ] all yellow color elements

// The real operation starts here

let sum = 0;

for (let i = 0; i < arr.length; i++) // 0) i=0<3 true , go inside the forloop

// 1) i=1<3 true, go inside the forloop

// 2) i=2<3 true, go inside the forloop

{

const leftDiagonalElements = arr[i][i]; // 0) arr[0][0] = 1

// 1) arr[1][1] = 5

// 2) arr[2][2] = 9

sum += leftDiagonalElements; // 0) sum = 1

// 1) sum => 4+5 = 9

// 2) sum => 14 +9 = 23

const rightDiagonalElements = arr[i][arr.length - 1 - i]; //0) arr[0][2] = 3

// 1) arr[1][1] = 5

// 2) arr[2][0] = 7

sum += rightDiagonalElements; // 0) sum => 1+3 =4

// 1) sum => 9+5 =14

// 2) sum => 23+7 = 30

// after this exit the forloop and console

the sum.

}

console.log(sum); // 2) 30

//////////////////////////////////////////////////////////////////////////////////////////////

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