[Hacker Rank]: Diagonal Difference solved ✓

Author: Gonzalo Diaz

docs/hackerrank/warmup/diagonalDifference.md

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+# [Diagonal Difference](https://www.hackerrank.com/challenges/diagonal-difference)
+
+Difficulty: #easy
+Category: #warmup
+
+Given a square matrix, calculate the absolute difference between the sums
+of its diagonals.
+For example, the square matrix $ arr $ is shown below:
+
+```text
+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
+space-separated integers ` arr[i][j] `.
+
+## Constraints
+
+$ -100 \leq $ ` arr[i][j] ` $ \leq 100 $
+
+## Output Format
+
+Return the absolute difference between the sums of the matrix's
+two diagonals as a single integer.
+
+## Sample Input
+
+```text
+3
+11 2 4
+4 5 6
+10 8 -12
+```
+
+Sample Output
+
+```text
+15
+```
+
+## Explanation
+
+The primary diagonal is:
+
+```text
+11
+   5
+     -12
+```
+
+Sum across the primary diagonal: 11 + 5 - 12 = 4
+The secondary diagonal is:
+
+```text
+     4
+   5
+10
+```
+
+Sum across the secondary diagonal: $ 4 + 5 + 10 = 19 $
+Difference: $ |4 - 19| = 15 $
+
+*Note*: $ |x| $ is the
+[absolute value](https://www.mathsisfun.com/numbers/absolute-value.html)
+of $ x $

src/pkg/hackerrank/warmup/diagonalDifference.go

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+/**
+ * @link Problem definition [[docs/hackerrank/warmup/diagonalDifference.md]]
+ */
+
+package hackerrank
+
+import (
+	"math"
+
+	utils "gon.cl/algorithm-exercises/src/utils"
+)
+
+func DiagonalDifference(arr [][]int) int {
+	diag1 := 0
+	diag2 := 0
+	last := len(arr) - 1
+
+	for i := 0; i < len(arr); i++ {
+		for j := 0; j < len(arr); j++ {
+			if i == j {
+				diag1 += arr[i][j]
+				diag2 += arr[last-i][j]
+			}
+		}
+	}
+
+	utils.Info("diag1 => %d", diag1)
+	utils.Info("diag2 => %d", diag2)
+
+	return int(math.Abs(float64(diag1 - diag2)))
+}

src/pkg/hackerrank/warmup/diagonalDifference_test.go

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+package hackerrank
+
+import (
+	"fmt"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestDiagonalDifference(t *testing.T) {
+
+	expectedSolution := 15
+	input := [][]int{
+		{11, 2, 4},
+		{4, 5, 6},
+		{10, 8, -12},
+	}
+
+	testname := fmt.Sprintf("solveMeFirst(%d) => %v \n", input, expectedSolution)
+	t.Run(testname, func(t *testing.T) {
+
+		ans := DiagonalDifference(input)
+		assert.Equal(t, expectedSolution, ans)
+	})
+}