[HackerRank] [C#] 1 Week Preparation Kit > Day 2 > Diagonal Difference

 

 

문제 : Diagonal Difference

사용언어 : C#

 

 

 

 

문제 내용

 

Given a square matrix, calculate the absolute difference between the sums of its diagonals.

For example, the square matrix arr is shown below:

1 2 3
4 5 6
9 8 9  

The left-to-right diagonal = 1 + 5 + 9 = 15. The right to left diagonal = 3 + 5 + 9 + 17. Their absolute difference is |15 - 17| = 2.

 

Function description

Complete the diagonalDifference function in the editor below.

diagonalDifference takes the following parameter:

• int arr[n][m]: an array of integers

 

Return

• int: the absolute diagonal difference

 

Input Format

The first line contains a single integer, n, the number of rows and columns in the square matrix arr.
Each of the next n lines describes a row,arr[i], and consists of n space-separated integers arr[i][j].

 

Constraints

• -100 <= arr[i][j] <= 100

 

Output Format

Return the absolute difference between the sums of the matrix's two diagonals as a single integer.

 

Sample Input

3
11 2 4
4 5 6
10 8 -12

Sample Output

15

Explanation

The primary diagonal is:

11
   5
     -12

Sum across the primary diagonal: 11 + 5 - 12 = 4

The secondary diagonal is:

     4
   5
10

Sum across the secondary diagonal: 4 + 5 + 10 = 19
Difference: |4 - 19| = 15

Note: |x| is the absolute value of x

 

 

 

 

 

 

 

내 풀이

이중 for문으로 숫자를 하나씩 돌면서 대각선을 확인했다. 

크기가 N * N 인 행렬이라고 했을 때, 

 

(위에서부터) 오른쪽 -> 왼쪽 방향의 대각선은 x랑 y가 같고, 

왼쪽 -> 오른쪽 방향의 대각선은 행렬 x, y의 합이 크기 N - 1이었다.

각각 구해서 계산하면 끝!

 

 

절댓값 구하기 : Abs()

 

 

    private static int plus;
    private static int minus;
    private static int length;
    
    public static int diagonalDifference(List<List<int>> arr)
    {
        length = arr.Count();
        for(int i = 0; i < length; ++i)
        {
            for(int j = 0; j < length; ++j)
            {
                if(i == j)
                {
                    plus += arr[i][j];
                }
                if(i + j == length - 1)
                {
                    minus += arr[i][j];
                }
            }
        }
        return Math.Abs(plus - minus);
    }

 

 

 

 

 

 

절댓값 구하기 / Abs()

public static int Abs(int num);

Math 클래스 안에 있는 함수.

사용 시에는 Math.Abs()로 썼다.