Created
July 5, 2016 05:33
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QuickSort implementation in Rust
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fn quicksort(array: &mut Vec<i32>) { | |
let mut stack = vec![]; | |
stack.push((0, array.len())); | |
while let Some(top) = stack.pop() { | |
let (start, end) = top; | |
match partition(array, start, end) { | |
None => continue, | |
Some(pivot_idx) => { | |
if pivot_idx > start { | |
// println!("{:?}", (start, pivot_idx)); | |
stack.push((start, pivot_idx)); | |
} | |
if end > (pivot_idx + 1) { | |
// println!("{:?}", (pivot_idx + 1, end)); | |
stack.push((pivot_idx + 1, end)); | |
} | |
// println!("{:?}", stack); | |
}, | |
} | |
} | |
} | |
fn swap(array: &mut Vec<i32>, a: usize, b: usize) { | |
let tmp = array[a]; | |
array[a] = array[b]; | |
array[b] = tmp; | |
} | |
fn scan_for_next_lt(array: &mut Vec<i32>, start: usize, pivot_idx: usize) -> usize { | |
let mut i = start; | |
let pivot = array[pivot_idx]; | |
while i > pivot_idx { | |
if array[i] < pivot { | |
return i | |
} | |
i -= 1; | |
} | |
i | |
} | |
fn scan_for_next_geq(array: &mut Vec<i32>, start: usize, pivot_idx: usize) -> usize { | |
let mut i = start; | |
let pivot = array[pivot_idx]; | |
while i < pivot_idx { | |
if array[i] >= pivot { | |
return i | |
} | |
i += 1; | |
} | |
i | |
} | |
fn partition(array: &mut Vec<i32>, start: usize, end: usize) -> Option<usize> { | |
if end - start <= 1 { | |
// println!("Partitioned: {:?}", &array[start..end]); | |
None | |
} else if end - start == 2 { | |
if array[start] > array[end-1] { | |
swap(array, start, end-1); | |
} | |
// println!("Partitioned: {:?}", &array[start..end]); | |
None | |
} else { | |
let pivot_idx = end - 1; | |
let mut lt_counter = 0; | |
let pivot = array[pivot_idx]; | |
for i in start..pivot_idx { | |
if array[i] < pivot { | |
lt_counter += 1; | |
} | |
} | |
let new_pivot_idx = start + lt_counter; | |
swap(array, pivot_idx, new_pivot_idx); | |
let mut top = end-1; | |
let mut bottom = start; | |
while bottom < new_pivot_idx && top > new_pivot_idx { | |
top = scan_for_next_lt(array, top, new_pivot_idx); | |
bottom = scan_for_next_geq(array, bottom, new_pivot_idx); | |
swap(array, top, bottom); | |
} | |
// println!("Partitioned: {:?}", &array[start..end]); | |
return Some(new_pivot_idx) | |
} | |
} | |
fn test_partition() { | |
let mut array = vec![3,7,8,5,2,1,9,5,4]; | |
let len = array.len(); | |
assert_eq!(partition(&mut array, 0, len), Some(3)); | |
assert_eq!(partition(&mut array, 0, len-1), Some(4)); | |
assert_eq!(partition(&mut array, 0, len-2), Some(6)); | |
assert_eq!(partition(&mut array, 0, len-3), Some(5)); | |
assert_eq!(partition(&mut array, 0, len-4), Some(4)); | |
assert_eq!(partition(&mut array, 0, len-5), Some(3)); | |
assert_eq!(partition(&mut array, 0, len-6), Some(1)); | |
assert_eq!(partition(&mut array, 0, len-7), None); | |
assert_eq!(partition(&mut array, 0, len-8), None); | |
assert_eq!(partition(&mut array, 0, len-9), None); | |
let mut array = vec![3,1,2,4,5,8,9,5,7]; | |
let len = array.len(); | |
assert_eq!(partition(&mut array, 0, 3), Some(1)); | |
assert_eq!(partition(&mut array, 4, len), Some(6)); | |
let mut array = vec![7, 9, 5, 8]; | |
let len = array.len(); | |
assert_eq!(partition(&mut array, 0, len), Some(2)); | |
println!("All partition tests passed!"); | |
} | |
fn test_quicksort() { | |
let mut to_sort = vec![3,7,8,5,2,1,9,5,4]; | |
quicksort(&mut to_sort); | |
assert_eq!(to_sort, [1, 2, 3, 4, 5, 5, 7, 8, 9]); | |
let mut to_sort = vec![]; | |
quicksort(&mut to_sort); | |
assert_eq!(to_sort, vec![]); | |
let mut to_sort = vec![1,2]; | |
quicksort(&mut to_sort); | |
assert_eq!(to_sort, vec![1,2]); | |
let mut to_sort = vec![2,1]; | |
quicksort(&mut to_sort); | |
assert_eq!(to_sort, vec![1,2]); | |
let mut to_sort = vec![1]; | |
quicksort(&mut to_sort); | |
assert_eq!(to_sort, vec![1]); | |
let mut to_sort = vec![6,5,3,1,8,7,2,4]; | |
quicksort(&mut to_sort); | |
assert_eq!(to_sort, vec![1,2,3,4,5,6,7,8]); | |
let mut to_sort = vec![6,5,3,1,8,7,2,4,9,10,11,12,13]; | |
quicksort(&mut to_sort); | |
assert_eq!(to_sort, vec![1,2,3,4,5,6,7,8,9,10,11,12,13]); | |
println!("All sorting tests passed!"); | |
} | |
fn main() { | |
test_partition(); | |
test_quicksort(); | |
} |
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