stdlib: Add an interior vector version of sort and a test case
This commit is contained in:
Patrick Walton
parent
b773f8d22b
commit
4c76bfdc1f
136
src/lib/sort.rs
136
src/lib/sort.rs
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@ -1,6 +1,9 @@
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import vec::len;
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import vec::slice;
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import ilen = ivec::len;
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import islice = ivec::slice;
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export ivector;
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export lteq;
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export merge_sort;
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export quick_sort;
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@ -130,6 +133,139 @@ fn quick_sort3[T](lteq[T] compare_func_lt, lteq[T] compare_func_eq,
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qsort3[T](compare_func_lt, compare_func_eq, arr, 0,
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(vec::len[T](arr) as int) - 1);
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}
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mod ivector {
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export merge_sort;
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export quick_sort;
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export quick_sort3;
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type lteq[T] = fn(&T, &T) -> bool;
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fn merge_sort[T](lteq[T] le, &T[] v) -> T[] {
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fn merge[T](lteq[T] le, &T[] a, &T[] b) -> T[] {
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let T[] rs = ~[];
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let uint a_len = ilen[T](a);
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let uint a_ix = 0u;
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let uint b_len = ilen[T](b);
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let uint b_ix = 0u;
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while (a_ix < a_len && b_ix < b_len) {
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if (le(a.(a_ix), b.(b_ix))) {
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rs += ~[a.(a_ix)];
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a_ix += 1u;
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} else { rs += ~[b.(b_ix)]; b_ix += 1u; }
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}
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rs += islice[T](a, a_ix, a_len);
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rs += islice[T](b, b_ix, b_len);
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ret rs;
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}
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let uint v_len = ilen[T](v);
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if (v_len <= 1u) { ret v; }
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let uint mid = v_len / 2u;
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let T[] a = islice[T](v, 0u, mid);
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let T[] b = islice[T](v, mid, v_len);
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ret merge[T](le, merge_sort[T](le, a), merge_sort[T](le, b));
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}
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fn swap[T](&T[mutable] arr, uint x, uint y) {
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auto a = arr.(x);
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arr.(x) = arr.(y);
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arr.(y) = a;
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}
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fn part[T](lteq[T] compare_func, &T[mutable] arr, uint left, uint right,
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uint pivot) -> uint {
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auto pivot_value = arr.(pivot);
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swap[T](arr, pivot, right);
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let uint storage_index = left;
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let uint i = left;
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while (i < right) {
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if (compare_func({ arr.(i) }, pivot_value)) {
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swap[T](arr, i, storage_index);
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storage_index += 1u;
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}
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i += 1u;
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}
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swap[T](arr, storage_index, right);
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ret storage_index;
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}
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fn qsort[T](lteq[T] compare_func, &T[mutable] arr, uint left,
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uint right) {
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if (right > left) {
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auto pivot = (left + right) / 2u;
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auto new_pivot = part[T](compare_func, arr, left, right, pivot);
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if (new_pivot == 0u) { ret; }
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qsort[T](compare_func, arr, left, new_pivot - 1u);
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qsort[T](compare_func, arr, new_pivot + 1u, right);
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}
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}
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fn quick_sort[T](lteq[T] compare_func, &T[mutable] arr) {
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if (ilen[T](arr) == 0u) { ret; }
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qsort[T](compare_func, arr, 0u, ilen[T](arr) - 1u);
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}
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// Based on algorithm presented by Sedgewick and Bentley here:
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// http://www.cs.princeton.edu/~rs/talks/QuicksortIsOptimal.pdf
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// According to these slides this is the algorithm of choice for
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// 'randomly ordered keys, abstract compare' & 'small number of key values'
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fn qsort3[T](lteq[T] compare_func_lt, lteq[T] compare_func_eq,
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&T[mutable] arr, int left, int right) {
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if (right <= left) { ret; }
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let T v = arr.(right);
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let int i = left - 1;
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let int j = right;
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let int p = i;
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let int q = j;
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while (true) {
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i += 1;
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while (compare_func_lt({ arr.(i) }, v)) { i += 1; }
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j -= 1;
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while (compare_func_lt(v, { arr.(j) })) {
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if (j == left) { break; }
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j -= 1;
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}
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if (i >= j) { break; }
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swap[T](arr, i as uint, j as uint);
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if (compare_func_eq({ arr.(i) }, v)) {
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p += 1;
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swap[T](arr, p as uint, i as uint);
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}
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if (compare_func_eq(v, { arr.(j) })) {
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q -= 1;
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swap[T](arr, j as uint, q as uint);
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}
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}
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swap[T](arr, i as uint, right as uint);
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j = i - 1;
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i += 1;
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let int k = left;
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while (k < p) {
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swap[T](arr, k as uint, j as uint);
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k += 1;
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j -= 1;
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if (k == ilen[T](arr) as int) { break; }
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}
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k = right - 1;
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while (k > q) {
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swap[T](arr, i as uint, k as uint);
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k -= 1;
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i += 1;
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if (k == 0) { break; }
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}
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qsort3[T](compare_func_lt, compare_func_eq, arr, left, j);
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qsort3[T](compare_func_lt, compare_func_eq, arr, i, right);
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}
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fn quick_sort3[T](lteq[T] compare_func_lt, lteq[T] compare_func_eq,
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&T[mutable] arr) {
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if (ilen[T](arr) == 0u) { ret; }
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qsort3[T](compare_func_lt, compare_func_eq, arr, 0,
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(ilen[T](arr) as int) - 1);
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}
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}
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// Local Variables:
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// mode: rust;
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// fill-column: 78;
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@ -0,0 +1,28 @@
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// xfail-stage0
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use std;
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fn check_sort(&int[] v1, &int[] v2) {
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auto len = std::ivec::len[int](v1);
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fn lteq(&int a, &int b) -> bool { ret a <= b; }
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auto f = lteq;
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auto v3 = std::sort::ivector::merge_sort[int](f, v1);
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auto i = 0u;
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while (i < len) { log v3.(i); assert (v3.(i) == v2.(i)); i += 1u; }
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}
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fn main() {
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{
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auto v1 = ~[3, 7, 4, 5, 2, 9, 5, 8];
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auto v2 = ~[2, 3, 4, 5, 5, 7, 8, 9];
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check_sort(v1, v2);
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}
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{ auto v1 = ~[1, 1, 1]; auto v2 = ~[1, 1, 1]; check_sort(v1, v2); }
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{ let int[] v1 = ~[]; let int[] v2 = ~[]; check_sort(v1, v2); }
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{ auto v1 = ~[9]; auto v2 = ~[9]; check_sort(v1, v2); }
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{
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auto v1 = ~[9, 3, 3, 3, 9];
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auto v2 = ~[3, 3, 3, 9, 9];
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check_sort(v1, v2);
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}
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}
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