Drop-Merge sort created and implemented by Emil Ernerfeldt.

Drop-Merge sort is an adaptive, unstable sorting algorithm designed for nearly-sorted data. An example use-case would be re-sorting an already sorted list after minor modifications.

Drop-Merge sort is especially useful for:

• Long lists (>10k elements)
• Where >80% of the data is already in-order
• The unsorted elements are evenly distributed.

Expected number of comparisons is O(N + K * log(K)) where K is the number of elements not in order. Expected memory usage is O(K). Works best when K < 0.2 * N. The out-of-order elements are expected to be randomly distributed (NOT clumped).

Examples

extern crate dmsort;

fn main() {
    let mut numbers : Vec<i32> = vec!(0, 1, 6, 7, 2, 3, 4, 5);

    // Sort with custom key:
    dmsort::sort_by_key(&mut numbers, |x| -x);
    assert_eq!(numbers, vec!(7, 6, 5, 4, 3, 2, 1, 0));

    // Sort with Ord trait:
    dmsort::sort(&mut numbers);
    assert_eq!(numbers, vec!(0, 1, 2, 3, 4, 5, 6, 7));

    // Sort with custom compare:
    dmsort::sort_by(&mut numbers, |a, b| b.cmp(a));
    assert_eq!(numbers, vec!(7, 6, 5, 4, 3, 2, 1, 0));
}