From 9975f9635cd1c2c58b6c1dbe47585859b0b1d573 Mon Sep 17 00:00:00 2001
From: Federico I <git@federicoigne.com>
Date: Tue, 17 Mar 2020 20:04:00 +0000
Subject: [rust] Difference of Squares

---
 difference-of-squares/src/lib.rs | 14 ++++++++++++++
 1 file changed, 14 insertions(+)
 create mode 100644 difference-of-squares/src/lib.rs

(limited to 'difference-of-squares/src/lib.rs')

diff --git a/difference-of-squares/src/lib.rs b/difference-of-squares/src/lib.rs
new file mode 100644
index 0000000..4599733
--- /dev/null
+++ b/difference-of-squares/src/lib.rs
@@ -0,0 +1,14 @@
+/// Implements square of Gauss' formula
+pub fn square_of_sum(n: u32) -> u32 {
+    (n * (n + 1) / 2).pow(2)
+}
+
+/// Implements the formula reported in Wolfram|Alpha at this
+/// [link](https://www.wolframalpha.com/input/?i=sum+of+squares&assumption=%7B%22F%22%2C+%22SumOfSquaresOfIntegers%22%2C+%22sumlowerlimit%22%7D+-%3E%221%22&assumption=%7B%22F%22%2C+%22SumOfSquaresOfIntegers%22%2C+%22sumupperlimit2%22%7D+-%3E%22n%22)
+pub fn sum_of_squares(n: u32) -> u32 {
+    n * (1 + n) * (1 + 2 * n) / 6
+}
+
+pub fn difference(n: u32) -> u32 {
+    square_of_sum(n) - sum_of_squares(n)
+}
-- 
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