m3

Author: growingspaghetti

src/lib.rs

@@ -1,5 +1,6 @@
 pub mod m1;
 pub mod m2;
+pub mod m3;
 
 #[cfg(test)]
 mod tests {

src/m2.rs

@@ -23,19 +23,16 @@ pub fn sum_of_even_fibonacci_sequence_less_than_4000000() -> i64 {
     let mut sum = 0;
     let mut prepre = 0i64;
     let mut pre = 0i64;
-    loop {
+    while pre < 4_000_000 {
+        if pre % 2 == 0 {
+            sum += pre;
+        }
         {
             let tuple = fib(prepre, pre);
             prepre = tuple.0;
             pre = tuple.1;
         }
         println!("num {}", pre);
-        if pre > 4_000_000 {
-            break;
-        }
-        if pre % 2 == 0 {
-            sum += pre;
-        }
     }
     sum
 }
@@ -69,20 +66,17 @@ pub fn sum_of_even_fibonacci_sequence_less_than_4000000_011_235_8() -> i64 {
     let mut preprepre = 0i64;
     let mut prepre = 1i64;
     let mut pre = 1i64;
-    loop {
+    while preprepre < 4_000_000 {
+        if preprepre % 2 == 0 {
+            sum += preprepre;
+        }
         {
             let tuple = fib(preprepre, prepre, pre);
             preprepre = tuple.0;
             prepre = tuple.1;
             pre = tuple.2
         }
         println!("num {}", preprepre);
-        if preprepre > 4_000_000 {
-            break;
-        }
-        if preprepre % 2 == 0 {
-            sum += preprepre;
-        }
     }
     sum
 }

src/m3.rs

@@ -0,0 +1,105 @@
+/// The prime factors of 13195 are 5, 7, 13 and 29.
+///
+/// What is the largest prime factor of the number 600851475143 ?
+///
+/// ```rust
+/// use self::project_euler::m3::largest_prime_factor_of_the_number_600851475143;
+/// assert_eq!(largest_prime_factor_of_the_number_600851475143(), 6857);
+/// ```
+pub fn largest_prime_factor_of_the_number_600851475143() -> u64 {
+    let mut n = 600851475143u64;
+    let mut diviser = 2u64;
+    let mut max_factor = 0u64;
+    // 16 -> 2 * 8 -> 2 * 4 -> 2 * 2 -> 2 * 1
+    // 21 -> 3 * 7 -> 7 * 1
+    // 28 -> 2 * 14 -> 2 * 7 -> 7 * 1
+    while n != 0 && n != 1 {
+        if n % diviser != 0 {
+            diviser += 1;
+        } else {
+            max_factor = n;
+            n = n / diviser;
+        }
+    }
+    max_factor
+}
+
+/// The prime factors of 13195 are 5, 7, 13 and 29.
+///
+/// What is the largest prime factor of the number 600851475143 ?
+///
+/// ```rust
+/// use self::project_euler::m3::largest_prime_factor_of_the_number_600851475143_skip_4_6_8_10_12;
+/// assert_eq!(largest_prime_factor_of_the_number_600851475143_skip_4_6_8_10_12(), 6857);
+/// ```
+pub fn largest_prime_factor_of_the_number_600851475143_skip_4_6_8_10_12() -> u64 {
+    let mut n = 600851475143u64;
+    let mut diviser = 3u64;
+    let mut max_factor;
+
+    if n % 2 == 0 {
+        n /= 2;
+        max_factor = 2;
+        while n % 2 == 0 {
+            n /= 2;
+        }
+    } else {
+        max_factor = 1;
+    }
+
+    while n > 1 {
+        if n % diviser == 0 {
+            n /= diviser;
+            max_factor = diviser;
+            while n % diviser == 0 {
+                n /= diviser
+            }
+        } else {
+            diviser += 2
+        }
+    }
+    max_factor
+}
+
+/// The prime factors of 13195 are 5, 7, 13 and 29.
+///
+/// What is the largest prime factor of the number 600851475143 ?
+///
+/// ```rust
+/// use self::project_euler::m3::largest_prime_factor_of_the_number_600851475143_skip_4_6_8_10_12_n_ab;
+/// assert_eq!(largest_prime_factor_of_the_number_600851475143_skip_4_6_8_10_12_n_ab(), 6857);
+/// ```
+pub fn largest_prime_factor_of_the_number_600851475143_skip_4_6_8_10_12_n_ab() -> u64 {
+    let mut n = 600851475143u64;
+    let mut diviser = 3u64;
+    let mut max_factor;
+
+    if n % 2 == 0 {
+        n /= 2;
+        max_factor = 2;
+        while n % 2 == 0 {
+            n /= 2;
+        }
+    } else {
+        max_factor = 1;
+    }
+
+    // n = 1 * n || n = a * b
+    //  in square,  n = sqrt(n) * sqrt(n)
+    //  pattern 1: a = sqrt(n) && b = sqrt(n)
+    //  pattern 2: a <= sqrt(n) || b <= sqrt(n)
+    //  impossible: a > sqrt(n) && b >= sqrt(n)
+    let a = (n as f64).sqrt() as u64;
+    while n > 1 && diviser <= a {
+        if n % diviser == 0 {
+            n /= diviser;
+            max_factor = diviser;
+            while n % diviser == 0 {
+                n /= diviser
+            }
+        } else {
+            diviser += 2
+        }
+    }
+    max_factor
+}