Merge pull request #9915 from zzyxyzz/indexOfMinMax

std.mem: add indexOfMin and indexOfMax

lib/std/mem.zig

@@ -2146,6 +2146,7 @@ fn testWriteIntImpl() !void {
 /// Returns the smallest number in a slice. O(n).
 /// `slice` must not be empty.
 pub fn min(comptime T: type, slice: []const T) T {
+    assert(slice.len > 0);
     var best = slice[0];
     for (slice[1..]) |item| {
         best = math.min(best, item);
@@ -2154,12 +2155,15 @@ pub fn min(comptime T: type, slice: []const T) T {
 }
 
 test "mem.min" {
-    try testing.expect(min(u8, "abcdefg") == 'a');
+    try testing.expectEqual(min(u8, "abcdefg"), 'a');
+    try testing.expectEqual(min(u8, "bcdefga"), 'a');
+    try testing.expectEqual(min(u8, "a"), 'a');
 }
 
 /// Returns the largest number in a slice. O(n).
 /// `slice` must not be empty.
 pub fn max(comptime T: type, slice: []const T) T {
+    assert(slice.len > 0);
     var best = slice[0];
     for (slice[1..]) |item| {
         best = math.max(best, item);
@@ -2168,7 +2172,99 @@ pub fn max(comptime T: type, slice: []const T) T {
 }
 
 test "mem.max" {
-    try testing.expect(max(u8, "abcdefg") == 'g');
+    try testing.expectEqual(max(u8, "abcdefg"), 'g');
+    try testing.expectEqual(max(u8, "gabcdef"), 'g');
+    try testing.expectEqual(max(u8, "g"), 'g');
+}
+
+/// Finds the smallest and largest number in a slice. O(n).
+/// Returns an anonymous struct with the fields `min` and `max`.
+/// `slice` must not be empty.
+pub fn minMax(comptime T: type, slice: []const T) struct { min: T, max: T } {
+    assert(slice.len > 0);
+    var minVal = slice[0];
+    var maxVal = slice[0];
+    for (slice[1..]) |item| {
+        minVal = math.min(minVal, item);
+        maxVal = math.max(maxVal, item);
+    }
+    return .{ .min = minVal, .max = maxVal };
+}
+
+test "mem.minMax" {
+    try testing.expectEqual(minMax(u8, "abcdefg"), .{ .min = 'a', .max = 'g' });
+    try testing.expectEqual(minMax(u8, "bcdefga"), .{ .min = 'a', .max = 'g' });
+    try testing.expectEqual(minMax(u8, "a"), .{ .min = 'a', .max = 'a' });
+}
+
+/// Returns the index of the smallest number in a slice. O(n).
+/// `slice` must not be empty.
+pub fn indexOfMin(comptime T: type, slice: []const T) usize {
+    assert(slice.len > 0);
+    var best = slice[0];
+    var index: usize = 0;
+    for (slice[1..]) |item, i| {
+        if (item < best) {
+            best = item;
+            index = i + 1;
+        }
+    }
+    return index;
+}
+
+test "mem.indexOfMin" {
+    try testing.expectEqual(indexOfMin(u8, "abcdefg"), 0);
+    try testing.expectEqual(indexOfMin(u8, "bcdefga"), 6);
+    try testing.expectEqual(indexOfMin(u8, "a"), 0);
+}
+
+/// Returns the index of the largest number in a slice. O(n).
+/// `slice` must not be empty.
+pub fn indexOfMax(comptime T: type, slice: []const T) usize {
+    assert(slice.len > 0);
+    var best = slice[0];
+    var index: usize = 0;
+    for (slice[1..]) |item, i| {
+        if (item > best) {
+            best = item;
+            index = i + 1;
+        }
+    }
+    return index;
+}
+
+test "mem.indexOfMax" {
+    try testing.expectEqual(indexOfMax(u8, "abcdefg"), 6);
+    try testing.expectEqual(indexOfMax(u8, "gabcdef"), 0);
+    try testing.expectEqual(indexOfMax(u8, "a"), 0);
+}
+
+/// Finds the indices of the smallest and largest number in a slice. O(n).
+/// Returns an anonymous struct with the fields `index_min` and `index_max`.
+/// `slice` must not be empty.
+pub fn indexOfMinMax(comptime T: type, slice: []const T) struct { index_min: usize, index_max: usize } {
+    assert(slice.len > 0);
+    var minVal = slice[0];
+    var maxVal = slice[0];
+    var minIdx: usize = 0;
+    var maxIdx: usize = 0;
+    for (slice[1..]) |item, i| {
+        if (item < minVal) {
+            minVal = item;
+            minIdx = i + 1;
+        }
+        if (item > maxVal) {
+            maxVal = item;
+            maxIdx = i + 1;
+        }
+    }
+    return .{ .index_min = minIdx, .index_max = maxIdx };
+}
+
+test "mem.indexOfMinMax" {
+    try testing.expectEqual(indexOfMinMax(u8, "abcdefg"), .{ .index_min = 0, .index_max = 6 });
+    try testing.expectEqual(indexOfMinMax(u8, "gabcdef"), .{ .index_min = 1, .index_max = 0 });
+    try testing.expectEqual(indexOfMinMax(u8, "a"), .{ .index_min = 0, .index_max = 0 });
 }
 
 pub fn swap(comptime T: type, a: *T, b: *T) void {