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Merge pull request #3844 from Snektron/sort-improvements

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Small sort improvements
This commit is contained in:
Andrew Kelley
2019-12-04 14:25:00 -05:00
committed by GitHub
parent 137cb32f5e 841a37ab59
commit 44e896f613
1 changed files with 108 additions and 8 deletions
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116
lib/std/sort.zig
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@@ -1189,24 +1189,124 @@ fn fuzzTest(rng: *std.rand.Random) void {
}
}
pub fn min(comptime T: type, items: []T, lessThan: fn (lhs: T, rhs: T) bool) T {
var i: usize = 0;
pub fn argMin(comptime T: type, items: []const T, lessThan: fn (lhs: T, rhs: T) bool) ?usize {
if (items.len == 0) {
return null;
}
var smallest = items[0];
for (items[1..]) |item| {
var smallest_index: usize = 0;
for (items[1..]) |item, i| {
if (lessThan(item, smallest)) {
smallest = item;
smallest_index = i + 1;
}
}
return smallest;
return smallest_index;
}
pub fn max(comptime T: type, items: []T, lessThan: fn (lhs: T, rhs: T) bool) T {
var i: usize = 0;
test "std.sort.argMin" {
testing.expectEqual(@as(?usize, null), argMin(i32, &[_]i32{}, asc(i32)));
testing.expectEqual(@as(?usize, 0), argMin(i32, &[_]i32{1}, asc(i32)));
testing.expectEqual(@as(?usize, 0), argMin(i32, &[_]i32{ 1, 2, 3, 4, 5 }, asc(i32)));
testing.expectEqual(@as(?usize, 3), argMin(i32, &[_]i32{ 9, 3, 8, 2, 5 }, asc(i32)));
testing.expectEqual(@as(?usize, 0), argMin(i32, &[_]i32{ 1, 1, 1, 1, 1 }, asc(i32)));
testing.expectEqual(@as(?usize, 0), argMin(i32, &[_]i32{ -10, 1, 10 }, asc(i32)));
testing.expectEqual(@as(?usize, 3), argMin(i32, &[_]i32{ 6, 3, 5, 7, 6 }, desc(i32)));
}
pub fn min(comptime T: type, items: []const T, lessThan: fn (lhs: T, rhs: T) bool) ?T {
const i = argMin(T, items, lessThan) orelse return null;
return items[i];
}
test "std.sort.min" {
testing.expectEqual(@as(?i32, null), min(i32, &[_]i32{}, asc(i32)));
testing.expectEqual(@as(?i32, 1), min(i32, &[_]i32{1}, asc(i32)));
testing.expectEqual(@as(?i32, 1), min(i32, &[_]i32{ 1, 2, 3, 4, 5 }, asc(i32)));
testing.expectEqual(@as(?i32, 2), min(i32, &[_]i32{ 9, 3, 8, 2, 5 }, asc(i32)));
testing.expectEqual(@as(?i32, 1), min(i32, &[_]i32{ 1, 1, 1, 1, 1 }, asc(i32)));
testing.expectEqual(@as(?i32, -10), min(i32, &[_]i32{ -10, 1, 10 }, asc(i32)));
testing.expectEqual(@as(?i32, 7), min(i32, &[_]i32{ 6, 3, 5, 7, 6 }, desc(i32)));
}
pub fn argMax(comptime T: type, items: []const T, lessThan: fn (lhs: T, rhs: T) bool) ?usize {
if (items.len == 0) {
return null;
}
var biggest = items[0];
for (items[1..]) |item| {
var biggest_index: usize = 0;
for (items[1..]) |item, i| {
if (lessThan(biggest, item)) {
biggest = item;
biggest_index = i + 1;
}
}
return biggest;
return biggest_index;
}
test "std.sort.argMax" {
testing.expectEqual(@as(?usize, null), argMax(i32, &[_]i32{}, asc(i32)));
testing.expectEqual(@as(?usize, 0), argMax(i32, &[_]i32{1}, asc(i32)));
testing.expectEqual(@as(?usize, 4), argMax(i32, &[_]i32{ 1, 2, 3, 4, 5 }, asc(i32)));
testing.expectEqual(@as(?usize, 0), argMax(i32, &[_]i32{ 9, 3, 8, 2, 5 }, asc(i32)));
testing.expectEqual(@as(?usize, 0), argMax(i32, &[_]i32{ 1, 1, 1, 1, 1 }, asc(i32)));
testing.expectEqual(@as(?usize, 2), argMax(i32, &[_]i32{ -10, 1, 10 }, asc(i32)));
testing.expectEqual(@as(?usize, 1), argMax(i32, &[_]i32{ 6, 3, 5, 7, 6 }, desc(i32)));
}
pub fn max(comptime T: type, items: []const T, lessThan: fn (lhs: T, rhs: T) bool) ?T {
const i = argMax(T, items, lessThan) orelse return null;
return items[i];
}
test "std.sort.max" {
testing.expectEqual(@as(?i32, null), max(i32, &[_]i32{}, asc(i32)));
testing.expectEqual(@as(?i32, 1), max(i32, &[_]i32{1}, asc(i32)));
testing.expectEqual(@as(?i32, 5), max(i32, &[_]i32{ 1, 2, 3, 4, 5 }, asc(i32)));
testing.expectEqual(@as(?i32, 9), max(i32, &[_]i32{ 9, 3, 8, 2, 5 }, asc(i32)));
testing.expectEqual(@as(?i32, 1), max(i32, &[_]i32{ 1, 1, 1, 1, 1 }, asc(i32)));
testing.expectEqual(@as(?i32, 10), max(i32, &[_]i32{ -10, 1, 10 }, asc(i32)));
testing.expectEqual(@as(?i32, 3), max(i32, &[_]i32{ 6, 3, 5, 7, 6 }, desc(i32)));
}
pub fn isSorted(comptime T: type, items: []const T, lessThan: fn (lhs: T, rhs: T) bool) bool {
var i: usize = 1;
while (i < items.len) : (i += 1) {
if (lessThan(items[i], items[i - 1])) {
return false;
}
}
return true;
}
test "std.sort.isSorted" {
testing.expect(isSorted(i32, &[_]i32{}, asc(i32)));
testing.expect(isSorted(i32, &[_]i32{10}, asc(i32)));
testing.expect(isSorted(i32, &[_]i32{ 1, 2, 3, 4, 5 }, asc(i32)));
testing.expect(isSorted(i32, &[_]i32{ -10, 1, 1, 1, 10 }, asc(i32)));
testing.expect(isSorted(i32, &[_]i32{}, desc(i32)));
testing.expect(isSorted(i32, &[_]i32{-20}, desc(i32)));
testing.expect(isSorted(i32, &[_]i32{ 3, 2, 1, 0, -1 }, desc(i32)));
testing.expect(isSorted(i32, &[_]i32{ 10, -10 }, desc(i32)));
testing.expect(isSorted(i32, &[_]i32{ 1, 1, 1, 1, 1 }, asc(i32)));
testing.expect(isSorted(i32, &[_]i32{ 1, 1, 1, 1, 1 }, desc(i32)));
testing.expectEqual(false, isSorted(i32, &[_]i32{ 5, 4, 3, 2, 1 }, asc(i32)));
testing.expectEqual(false, isSorted(i32, &[_]i32{ 1, 2, 3, 4, 5 }, desc(i32)));
testing.expect(isSorted(u8, "abcd", asc(u8)));
testing.expect(isSorted(u8, "zyxw", desc(u8)));
testing.expectEqual(false, isSorted(u8, "abcd", desc(u8)));
testing.expectEqual(false, isSorted(u8, "zyxw", asc(u8)));
testing.expect(isSorted(u8, "ffff", asc(u8)));
testing.expect(isSorted(u8, "ffff", desc(u8)));
}