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| use std::cmp::Ordering;
#[test] fn test_netherlands_flag_partition() { let mut array = [7, 1, 2, 0, 8, 5, 3, 9, 2, 6, 5, 1, 0, 8, 7, 4]; assert_eq!( array.netherlands_flag_partition(2), NetherlandsFlagResult::Three(4, 6) ); assert_eq!( array.netherlands_flag_partition(7), NetherlandsFlagResult::Three(11, 13) ); assert_eq!( array.netherlands_flag_partition(-1), NetherlandsFlagResult::Greater ); assert_eq!( array.netherlands_flag_partition(0), NetherlandsFlagResult::ValueStart(2) ); assert_eq!( array.netherlands_flag_partition(10), NetherlandsFlagResult::Less ); assert_eq!( array.netherlands_flag_partition(9), NetherlandsFlagResult::ValueEnd(15) );
let mut array = [2, 2, 2, 2, 2]; assert_eq!( array.netherlands_flag_partition(2), NetherlandsFlagResult::Equal ); }
#[derive(Debug, Eq, PartialEq)] pub enum NetherlandsFlagResult { Three(usize, usize), ValueStart(usize), ValueEnd(usize), Less, Greater, Equal, }
pub trait NetherlandsFlagPartition<T> { fn netherlands_flag_partition(&mut self, value: T) -> NetherlandsFlagResult; }
impl<T: Ord> NetherlandsFlagPartition<T> for [T] { fn netherlands_flag_partition(&mut self, value: T) -> NetherlandsFlagResult { let len = self.len(); let mut left = None; let mut right = None; let mut i = 0; while i < right.unwrap_or(len) { match self[i].cmp(&value) { Ordering::Less => { match left { None => { self.swap(0, i); left = Some(0); } Some(left_value) => { let new_left = left_value + 1; self.swap(new_left, i); left = Some(new_left); } } i += 1; } Ordering::Equal => { i += 1; } Ordering::Greater => { match right { None => { self.swap(len - 1, i); right = Some(len - 1); } Some(right_value) => { let new_right = right_value - 1; self.swap(new_right, i); right = Some(new_right); } }
} } }
match (left.map(|v| v + 1), right) { (None, Some(i)) => { if i == 0 { NetherlandsFlagResult::Greater } else { NetherlandsFlagResult::ValueStart(i) } } (Some(i), None) => { if i >= self.len() { NetherlandsFlagResult::Less } else { NetherlandsFlagResult::ValueEnd(i) } } (Some(i), Some(j)) => { if i >= self.len() { NetherlandsFlagResult::Greater } else { NetherlandsFlagResult::Three(i, j) } } (None, None) => NetherlandsFlagResult::Equal, } } }
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