leetcode 3: string usage in go & a naive answer

go/cmd/demo.go

@@ -2,8 +2,8 @@ package cmd
 
 import (
 	"fmt"
-
 	"play/demo"
+	"unicode/utf8"
 
 	"github.com/spf13/cobra"
 )
@@ -21,7 +21,24 @@ var demoCmd = &cobra.Command{
 }
 
 func demoMain() {
-	fmt.Println("abs ", demo.AbsIf(-2), demo.AbsBitwise(-2))
-	fmt.Println("abs ", demo.AbsIf(-9223372036854775808), demo.AbsBitwise(-9223372036854775808))
-	fmt.Println("abs ", demo.AbsIf(-9223372036854775807), demo.AbsBitwise(9223372036854775807))
+	s := "中文🏄💾"
+	for i, v := range s {
+		fmt.Printf("%d %c %v 0x%05X\n", i, v, v, v)
+	}
+	fmt.Println("len s : ", len(s), utf8.RuneCountInString(s))
+
+	vs := []rune(s)
+	fmt.Println(vs)
+
+	fn := func(s string, n int) {
+		if m := demo.LengthOfLongestSubstring(s); m != n {
+			fmt.Printf("error %s: should be %d, got %d\n", s, n, m)
+		} else {
+			fmt.Println("ok", s, n, m)
+		}
+	}
+	// fn("bbb", 1)
+	// fn("abcad", 3)
+	// fn("pwwkew", 3)
+	fn("dvdf", 3)
 }

go/demo/leetcode.go

@@ -1,6 +1,9 @@
 package demo
 
-import "math/bits"
+import (
+	"math/bits"
+	"unicode/utf8"
+)
 
 func TwoSum(nums []int, target int) []int {
 	dict := make(map[int]int, len(nums))
@@ -153,3 +156,35 @@ func NumToList(n int) *ListNode {
 
 	return head
 }
+
+func LengthOfLongestSubstring(s string) int {
+	sl := utf8.RuneCountInString(s)
+
+	vs := []rune(s)
+
+	dict := make(map[rune]int)
+	count := 0
+	max := 0
+
+	for i := 0; i < sl; {
+		v := vs[i]
+
+		if b, has := dict[v]; has {
+			count = 0
+			dict = make(map[rune]int)
+			i = b + 1
+			if max > sl-i {
+				break
+			}
+		} else {
+			dict[v] = i
+			count += 1
+			i += 1
+		}
+
+		if count > max {
+			max = count
+		}
+	}
+	return max
+}

go/demo/leetcode_test.go

@@ -58,3 +58,15 @@ func TestAddTwoNumbers(t *testing.T) {
 	testFn(10, 235)
 	testFn(9999, 2)
 }
+
+func TestLengthOfLongestSubstring(t *testing.T) {
+	fn := func(s string, n int) {
+		if LengthOfLongestSubstring(s) != n {
+			t.Fail()
+		}
+	}
+	fn("bbb", 1)
+	fn("abcabcbb", 3)
+	fn("pwwkew", 3)
+	fn("dvdf", 3)
+}