Data Structure & Algorithms
DSA
Arrays 2D Matrices
Main Diagonal Sum

# Main Diagonal Sum

## Problem Description

You are given a N X N integer matrix. You have to find the sum of all the main diagonal elements of A. Main diagonal of a matrix A is a collection of elements A[i, j] such that i = j.

### Problem Constraints

``````1 <= N <= 10^3
-1000 <= A[i][j] <= 1000``````

### Input Format

``There are 1 lines in the input. First 2 integers R, C are the number of rows and columns. Then R * C integers follow corresponding to the rowwise numbers in the 2D array A.``

### Output Format

``Return an integer denoting the sum of main diagonal elements.``

### Example Input

``````Input 1:
3 3 1 -2 -3 -4 5 -6 -7 -8 9

Input 2:
2 2 3 2 2 3``````

### Example Output

``````Output 1:
15

Output 2:
6``````

### Example Explanation

``````Explanation 1:
The size of matrix is 3.
So, considering the indexing from 0.
Main diagonal elements will be A, A and A
A + A + A = 1 + 5 + 9 = 15

Explanation 2:
The size of matrix is 2.
So, considering the indexing from 0.
Main diagonal elements will be A and A.
A + A = 3 + 3 = 6``````

### Output

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