From 7690516566e5565ca73c87f3514ed8a155c20189 Mon Sep 17 00:00:00 2001
From: Gonzalo Diaz <devel@gon.cl>
Date: Wed, 10 Sep 2025 19:38:19 -0300
Subject: [PATCH] =?UTF-8?q?[Hacker=20Rank]:=20Warmup:=20Diagonal=20Differe?=
 =?UTF-8?q?nce.=20Solved=20=E2=9C=85.?=
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---
 docs/hackerrank/warmup/diagonal_difference.md | 86 +++++++++++++++++++
 src/hackerrank/warmup/diagonal_difference.rs  | 19 ++++
 src/hackerrank/warmup/mod.rs                  |  1 +
 .../warmup/diagonal_difference.testcases.json | 10 +++
 .../hackerrank/warmup/diagonal_difference.rs  | 31 +++++++
 tests/hackerrank/warmup/mod.rs                |  1 +
 6 files changed, 148 insertions(+)
 create mode 100644 docs/hackerrank/warmup/diagonal_difference.md
 create mode 100644 src/hackerrank/warmup/diagonal_difference.rs
 create mode 100644 tests/data/hackerrank/warmup/diagonal_difference.testcases.json
 create mode 100644 tests/hackerrank/warmup/diagonal_difference.rs

diff --git a/docs/hackerrank/warmup/diagonal_difference.md b/docs/hackerrank/warmup/diagonal_difference.md
new file mode 100644
index 0000000..496e3a7
--- /dev/null
+++ b/docs/hackerrank/warmup/diagonal_difference.md
@@ -0,0 +1,86 @@
+# [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 $
diff --git a/src/hackerrank/warmup/diagonal_difference.rs b/src/hackerrank/warmup/diagonal_difference.rs
new file mode 100644
index 0000000..deb3e05
--- /dev/null
+++ b/src/hackerrank/warmup/diagonal_difference.rs
@@ -0,0 +1,19 @@
+// @link Problem definition [[docs/hackerrank/warmup/diagonal_difference.md]]
+
+pub fn diagonal_difference(arr: &[Vec<i32>]) -> i32 {
+  let mut diag1 = 0;
+  let mut diag2 = 0;
+
+  let last = arr.len() - 1;
+  for (i, row) in arr.iter().enumerate() {
+    for(j, &value) in row.iter().enumerate() {
+      if i == j {
+        diag1 += value;
+        diag2 += arr[last - i][j];
+      }
+    }
+  }
+
+  (diag1 - diag2).abs()
+}
+
diff --git a/src/hackerrank/warmup/mod.rs b/src/hackerrank/warmup/mod.rs
index 2e5b07f..e73f9c1 100644
--- a/src/hackerrank/warmup/mod.rs
+++ b/src/hackerrank/warmup/mod.rs
@@ -2,3 +2,4 @@ pub mod solve_me_first;
 pub mod simple_array_sum;
 pub mod compare_triplets;
 pub mod a_very_big_sum;
+pub mod diagonal_difference;
diff --git a/tests/data/hackerrank/warmup/diagonal_difference.testcases.json b/tests/data/hackerrank/warmup/diagonal_difference.testcases.json
new file mode 100644
index 0000000..ea2b143
--- /dev/null
+++ b/tests/data/hackerrank/warmup/diagonal_difference.testcases.json
@@ -0,0 +1,10 @@
+[
+  { "matrix":
+    [
+      [11, 2, 4],
+      [4, 5, 6],
+      [10, 8, -12]
+    ],
+    "expected": 15
+  }
+]
diff --git a/tests/hackerrank/warmup/diagonal_difference.rs b/tests/hackerrank/warmup/diagonal_difference.rs
new file mode 100644
index 0000000..185e134
--- /dev/null
+++ b/tests/hackerrank/warmup/diagonal_difference.rs
@@ -0,0 +1,31 @@
+use exercises::hackerrank::warmup::diagonal_difference::diagonal_difference;
+use once_cell::sync::Lazy;
+use serde::Deserialize;
+
+use crate::common;
+use common::utils::load_json;
+
+#[cfg(test)]
+mod tests {
+  use super::*;
+
+  #[derive(Debug, Deserialize)]
+  struct DiagonalDifferenceTestCase {
+      matrix: Vec<Vec<i32>>,
+      expected: i32
+  }
+
+  static TEST_DATA: Lazy<Vec<DiagonalDifferenceTestCase>> =
+    Lazy::new(|| load_json("tests/data/hackerrank/warmup/diagonal_difference.testcases.json"));
+
+  #[test]
+  fn test_diagonal_difference() {
+    println!("Testing hackerrank::warmup::diagonal_difference::diagonal_difference()");
+
+    for test_case in TEST_DATA.iter() {
+      let slice: &[Vec<i32>] = &test_case.matrix;
+      let result = diagonal_difference(slice);
+      assert_eq!(result, test_case.expected);
+    }
+  }
+}
diff --git a/tests/hackerrank/warmup/mod.rs b/tests/hackerrank/warmup/mod.rs
index 2e5b07f..e73f9c1 100644
--- a/tests/hackerrank/warmup/mod.rs
+++ b/tests/hackerrank/warmup/mod.rs
@@ -2,3 +2,4 @@ pub mod solve_me_first;
 pub mod simple_array_sum;
 pub mod compare_triplets;
 pub mod a_very_big_sum;
+pub mod diagonal_difference;