[rust] Difference of Squares

1 files changed, 14 insertions, 0 deletions

diff --git a/difference-of-squares/src/lib.rs b/difference-of-squares/src/lib.rs
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+++ b/difference-of-squares/src/lib.rs
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+/// 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)
+}