1-8

Author: chubei

.gitignore

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+/target

Cargo.lock

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+[package]
+name = "project_euler"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]

Cargo.toml

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+fn main() {
+    let mut result = 0;
+    for i in 1..1000 {
+        if i % 3 == 0 || i % 5 == 0 {
+            result += i;
+        }
+    }
+    println!("{}", result);
+}

src/bin/1.rs

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+fn main() {
+    let mut result = 0;
+    let mut a = 1;
+    let mut b = 2;
+    while b <= 4_000_000 {
+        if b % 2 == 0 {
+            result += b;
+        }
+        let c = a + b;
+        a = b;
+        b = c;
+    }
+    println!("{}", result);
+}

src/bin/2.rs

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+use project_euler::*;
+
+fn main() {
+    let mut n = 600851475143;
+    let mut factor = get_smallest_prime_factor(n);
+    while factor != n {
+        n /= factor;
+        factor = get_smallest_prime_factor(n);
+    }
+    println!("{}", factor);
+}

src/bin/3.rs

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+use project_euler::*;
+
+fn main() {
+    let mut result = 0;
+    for i in 100..1000 {
+        for j in i..1000 {
+            let product = i * j;
+            if is_palindromic(product) {
+                result = result.max(product);
+            }
+        }
+    }
+    println!("{}", result);
+}

src/bin/4.rs

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+fn main() {
+    let mut nums: Vec<_> = (2..21).collect();
+    let mut result = 1;
+    let mut index = 0;
+    while index < nums.len() {
+        let num = nums[index];
+        result *= num;
+        index += 1;
+        for n in &mut nums[index..] {
+            if *n % num == 0 {
+                *n /= num;
+            }
+        }
+    }
+    println!("{}", result);
+}

src/bin/5.rs

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+fn main() {
+    let mut sum = 0;
+    let mut square_sum = 0;
+    for n in 1..=100 {
+        sum += n;
+        square_sum += n * n;
+    }
+    println!("{}", sum * sum - square_sum);
+}

src/bin/6.rs

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+use project_euler::*;
+
+fn main() {
+    let mut n = 2;
+    let mut count = 0;
+    while count < 10_001 {
+        if is_prime(n) {
+            println!("{}", n);
+            count += 1;
+        }
+        n += 1;
+    }
+    println!("{}", n - 1);
+}

src/bin/7.rs

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+const LEN: usize = 13;
+
+fn find_nonzero_product(seq: &[u8], index: usize) -> (u64, usize) {
+    let mut result = 1u64;
+    if index + LEN >= seq.len() {
+        return (0, seq.len());
+    }
+    for i in index..(index + LEN) {
+        let n = seq[i];
+        if n == b'0' {
+            return find_nonzero_product(seq, i + 1);
+        }
+        result *= (n - b'0') as u64
+    }
+    (result, index + LEN)
+}
+
+fn main() {
+    let seq = b"7316717653133062491922511967442657474235534919493496983520312774506326239578318016984801869478851843858615607891129494954595017379583319528532088055111254069874715852386305071569329096329522744304355766896648950445244523161731856403098711121722383113622298934233803081353362766142828064444866452387493035890729629049156044077239071381051585930796086670172427121883998797908792274921901699720888093776657273330010533678812202354218097512545405947522435258490771167055601360483958644670632441572215539753697817977846174064955149290862569321978468622482839722413756570560574902614079729686524145351004748216637048440319989000889524345065854122758866688116427171479924442928230863465674813919123162824586178664583591245665294765456828489128831426076900422421902267105562632111110937054421750694165896040807198403850962455444362981230987879927244284909188845801561660979191338754992005240636899125607176060588611646710940507754100225698315520005593572972571636269561882670428252483600823257530420752963450";
+    let (mut current, mut index) = find_nonzero_product(seq, 0);
+    let mut result = current;
+    while index < seq.len() {
+        if seq[index] == b'0' {
+            let product = find_nonzero_product(seq, index + 1);
+            current = product.0;
+            index = product.1;
+        } else {
+            current /= (seq[index - LEN] - b'0') as u64;
+            current *= (seq[index] - b'0') as u64;
+            index += 1;
+        }
+        result = result.max(current);
+    }
+    println!("{}", result);
+}

src/bin/8.rs

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+pub fn get_smallest_prime_factor(n: u64) -> u64 {
+    for i in 2..=(n / 2) {
+        if n % i == 0 {
+            return i;
+        }
+    }
+    n
+}
+
+pub fn is_prime(n: u64) -> bool {
+    get_smallest_prime_factor(n) == n
+}
+
+pub fn is_palindromic(n: u64) -> bool {
+    is_palindromic_chars(number_to_reverse_chars(n))
+}
+
+pub fn number_to_reverse_chars(mut n: u64) -> Vec<u8> {
+    let mut result = vec![];
+    while n > 0 {
+        result.push((n % 10) as u8);
+        n /= 10;
+    }
+    result
+}
+
+pub fn is_palindromic_chars(chars: Vec<u8>) -> bool {
+    let end = chars.len() / 2 + 1;
+    for i in 0..end {
+        if chars[i] != chars[chars.len() - i - 1] {
+            return false;
+        }
+    }
+    true
+}