m1

Author: growingspaghetti

.gitignore

@@ -0,0 +1,2 @@
+/target
+Cargo.lock

Cargo.toml

@@ -0,0 +1,9 @@
+[package]
+name = "project-euler"
+version = "0.1.0"
+authors = ["Ryoji <[email protected]>"]
+edition = "2018"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]

README.md

@@ -0,0 +1,4 @@
+```
+cargo new project-euler --lib
+touch src/main.rs
+```

src/lib.rs

@@ -0,0 +1,10 @@
+pub mod m1;
+pub mod m2;
+
+#[cfg(test)]
+mod tests {
+    #[test]
+    fn it_works() {
+        assert_eq!(2 + 2, 4);
+    }
+}

src/m1.rs

@@ -0,0 +1,49 @@
+/// If we list all the natural numbers below 10 that are multiples of 3 or 5, we get 3, 5, 6 and 9. The sum of these multiples is 23.
+///
+/// Find the sum of all the multiples of 3 or 5 below 1000.
+///
+/// ```rust
+/// use self::project_euler::m1::sum_of_all_the_multiples_of_3_or_5_below_1000;
+/// assert_eq!(sum_of_all_the_multiples_of_3_or_5_below_1000(), 233168);
+/// ```
+pub fn sum_of_all_the_multiples_of_3_or_5_below_1000() -> i32 {
+    let mut sum = 0;
+    for x in 0..1000 {
+        if x % 3 == 0 || x % 5 == 0 {
+            sum += x;
+        }
+    }
+    sum
+}
+
+/// If we list all the natural numbers below 10 that are multiples of 3 or 5, we get 3, 5, 6 and 9. The sum of these multiples is 23.
+///
+/// Find the sum of all the multiples of 3 or 5 below 1000.
+///
+/// ```rust
+/// use self::project_euler::m1::sum_of_all_the_multiples_of_3_or_5_below_1000_iter;
+/// assert_eq!(sum_of_all_the_multiples_of_3_or_5_below_1000_iter(), 233168);
+/// ```
+pub fn sum_of_all_the_multiples_of_3_or_5_below_1000_iter() -> i32 {
+    (0..1000).filter(|&x| x % 5 == 0 || x % 3 == 0).sum()
+}
+
+/// If we list all the natural numbers below 10 that are multiples of 3 or 5, we get 3, 5, 6 and 9. The sum of these multiples is 23.
+///
+/// Find the sum of all the multiples of 3 or 5 below 1000.
+///
+/// ```rust
+/// use self::project_euler::m1::sum_of_all_the_multiples_of_3_or_5_below_1000_arithmetic_series;
+/// assert_eq!(sum_of_all_the_multiples_of_3_or_5_below_1000_arithmetic_series(), 233168);
+/// ```
+pub fn sum_of_all_the_multiples_of_3_or_5_below_1000_arithmetic_series() -> i32 {
+    // 0  3  6  9 .. 999 = 3 * [0 1 2 3 ... 333] = 3 * (0+333 #doubling) * 334#n / 2#halving
+    // 0  5 10 15 .. 995 = 5 * [0 1 2 3 ... 199] = 5 * (0+199 #doubling) * 200#n / 2#halving
+    // 0 15 30 45 .. 999-999%15#last = 15 * [0 1 2 3 ... last/15]
+    let arithmetic_series = |common_difference: i32| -> i32 {
+        let last = 999 - 999 % common_difference;
+        let n = last / common_difference + 1;
+        last * n / 2
+    };
+    arithmetic_series(3) + arithmetic_series(5) - arithmetic_series(15)
+}

src/m2.rs

@@ -0,0 +1 @@
+

src/main.rs

@@ -0,0 +1 @@
+fn main() {}