IntFieldsIter combines field iteration and int parsing

Author: aaronbee

day04/day04.go

@@ -49,12 +49,12 @@ func matches(s string) int {
 		panic(fmt.Errorf("unexpected card: %q", card))
 	}
 	boolSet := [101]bool{}
-	aoc2023.FieldsIter(winners, func(s string) {
-		boolSet[aoc2023.Atoi(s)] = true
+	aoc2023.IntFieldsIter(winners, func(v int) {
+		boolSet[v] = true
 	})
 	var count int
-	aoc2023.FieldsIter(plays, func(s string) {
-		if boolSet[aoc2023.Atoi(s)] {
+	aoc2023.IntFieldsIter(plays, func(v int) {
+		if boolSet[v] {
 			count++
 		}
 	})

utils.go

@@ -36,17 +36,19 @@ func Atoi(s string) int {
 	return i
 }
 
-func FieldsIter(s string, fn func(s string)) {
+func IntFieldsIter(s string, fn func(i int)) {
 	i := 0
 	for {
 		for ; i < len(s) && s[i] == ' '; i++ {
 		}
 		beg := i
+		var v int
 		for ; i < len(s) && s[i] != ' '; i++ {
+			v = v*10 + int(s[i]-'0')
 		}
 		if beg == i {
 			return
 		}
-		fn(s[beg:i])
+		fn(v)
 	}
 }

utils_test.go

@@ -5,15 +5,15 @@ import (
 	"testing"
 )
 
-func TestFieldsIter(t *testing.T) {
-	var ss []string
-	join := func(s string) { ss = append(ss, s) }
-	FieldsIter("0", join)
-	if !slices.Equal(ss, []string{"0"}) {
+func TestIntFieldsIter(t *testing.T) {
+	var ss []int
+	join := func(v int) { ss = append(ss, v) }
+	IntFieldsIter("0", join)
+	if !slices.Equal(ss, []int{0}) {
 		t.Error(ss)
 	}
-	FieldsIter("  1 2 3  4 56 ", join)
-	if !slices.Equal(ss, []string{"0", "1", "2", "3", "4", "56"}) {
+	IntFieldsIter("  1 2 3  4 56 ", join)
+	if !slices.Equal(ss, []int{0, 1, 2, 3, 4, 56}) {
 		t.Error(ss)
 	}
 }