let swap tab a b =
    if a <> b then
    (
        let t = tab.(a) in
        tab.(a) <- tab.(b);
        tab.(b) <- t
    )
in
let msort tab a b =
    let m = b / 2 in
    let li = ref a in
    let ri = ref (a + m) in
    let s = ref 0 in
    for i = 0 to (b - 1) do
        if tab.(!li) > tab.(!ri) then
        (
            swap tab (a + i) (!ri);
            ri := !ri + 1;
        ) else
        (
            swap tab (a + i) (!li);
            if (!li + 1 < !ri) then
                li := !li + 1
            else
                li := a + i + 1
        )
    done
in
let rsort tab a b =
    if b > 1 then
    (
        let m = b / 2;
        rsort tab a m;
        rsort tab (a + m) (b - m);
        msort tab a b
    )
in
let sort tab =
    rsort tab 0 (length tab)
in