algos/src/quick_sort.rs

use std::cmp::PartialOrd;


fn median_of_three<T: PartialOrd + Copy>( v: &[T]) -> usize {
	if v.len() < 3 {
		return 0;
	}

	let left = 0;
	let middle = if v.len() % 2 == 0 {
		v.len() / 2 - 1
	} else {
		v.len() / 2
	};
	let right = v.len() - 1;
	let mut values = vec![v[left], v[middle], v[right]];
	bubble_sort(&mut values);
	let median = values[1];
	if median == v[left] {
		return left;
	} else if median == v[middle] {
		return middle;
	} else if median == v[right]{
		return right;
	} else {
		panic!("Did not find median in values!");
	}
}

fn bubble_sort<T: PartialOrd>( v: &mut [T]) -> () {
	let mut unsorted = true;
	if v.len() <= 1 {
		return
	}
	while unsorted {
		unsorted = false;
		for i in 0..v.len() - 1 {
			if v[i] > v[i + 1] {
				v.swap(i, i + 1);
				unsorted = true;
			}
		}
	}

}

pub fn quick_sort<T: PartialOrd + Copy>( v: &mut [T], comp_acc: &mut usize) -> () {
    if v.len() <= 1 {
    	return;
    }
    // let pivot_index = 0;
    // let pivot_index = v.len() - 1;
    let pivot_index = median_of_three(&v);
    let mut i = 1;
    v.swap(0, pivot_index);
    for j in 1..v.len() {
    	if v[j] < v[0] {
    		v.swap(i, j);
    		i += 1;
    	}
    }
    v.swap(0, i - 1);
    quick_sort(&mut v[..i - 1], comp_acc);
    quick_sort(&mut v[i..], comp_acc);

    *comp_acc += v[..i - 1].len();
    *comp_acc += v[i..].len();
}