string-to-integer-atoi

Author: vfedorovatlas

string-to-integer-atoi/main.go

@@ -0,0 +1,55 @@
+package atoi
+
+import (
+	"strings"
+)
+
+const intMax = 2147483647
+const intMin = -2147483648
+
+func myAtoi(str string) int {
+	prefix := 1
+	str = strings.TrimSpace(str)
+	l := len(str)
+	if l == 0 {
+		return 0
+	}
+	if str[0] == '-' || str[0] == '+' {
+		if str[0] == '-' {
+			prefix = -1
+		}
+		str = str[1:]
+		l = len(str)
+		if l < 1 {
+			return 0
+		}
+	}
+	num := 0
+	i := 0
+	for {
+		c := byte(str[i])
+		c = c - '0'
+		if c > 9 {
+			break
+		}
+		num = num*10 + int(c)
+		i++
+		if i > 10 && i < l {
+			if prefix > 0 {
+				return intMax
+			}
+			return intMin
+		}
+		if i >= l {
+			break
+		}
+	}
+	res := prefix * num
+	if res >= intMax {
+		return intMax
+	}
+	if res <= intMin {
+		return intMin
+	}
+	return prefix * num
+}

string-to-integer-atoi/main_test.go

@@ -0,0 +1,96 @@
+package atoi
+
+import (
+	"fmt"
+	"math"
+	"strconv"
+	"testing"
+)
+
+func TestMyAtoi(t *testing.T) {
+	testCases := []struct {
+		Input  string
+		Output int
+	}{
+		{
+			Input:  "",
+			Output: 0,
+		},
+		{
+			Input:  "-",
+			Output: 0,
+		},
+		{
+			Input:  "+",
+			Output: 0,
+		},
+		{
+			Input:  "0",
+			Output: 0,
+		},
+		{
+			Input:  "123",
+			Output: 123,
+		},
+		{
+			Input:  "-1",
+			Output: -1,
+		},
+		{
+			Input:  "1",
+			Output: 1,
+		},
+		{
+			Input:  "2147483648",
+			Output: 2147483647,
+		},
+		{
+			Input:  strconv.Itoa(math.MinInt32),
+			Output: -2147483648,
+		},
+		{
+			Input:  "    010",
+			Output: 10,
+		},
+		{
+			Input:  "1a",
+			Output: 1,
+		},
+		{
+			Input:  "  -0012a42",
+			Output: -12,
+		},
+		{
+			Input:  "  -a1",
+			Output: 0,
+		},
+		{
+			Input:  "9223372036854775809",
+			Output: 2147483647,
+		},
+		{
+			Input:  "             ",
+			Output: 0,
+		},
+		{
+			Input:  "   -1123u3761867",
+			Output: -1123,
+		},
+		{
+			Input:  "      -11919730356x",
+			Output: -2147483648,
+		},
+		{
+			Input:  "  -1010023630o4",
+			Output: -1010023630,
+		},
+	}
+	for _, test := range testCases {
+		t.Run(fmt.Sprintf("input=%s output=%d", test.Input, test.Output), func(t *testing.T) {
+			res := myAtoi(test.Input)
+			if res != test.Output {
+				t.Errorf("wanted %d, but got %d", test.Output, res)
+			}
+		})
+	}
+}