string_to_integer

Author: hitzzc

README.md

@@ -9,5 +9,6 @@ leetcode for golang
 #### [5. longest palindromic substring](https://github.com/hitzzc/go-leetcode/tree/master/longest_palindromic_substring)
 #### [6. zigzag conversion](https://github.com/hitzzc/go-leetcode/tree/master/zigzag_conversion)
 #### [7. reverse integer](https://github.com/hitzzc/go-leetcode/tree/master/reverse_integer)
+#### [8. string to integer](https://github.com/hitzzc/go-leetcode/tree/master/string_to_integer)
 
 

string_to_integer/string_to_integer.go

@@ -0,0 +1,52 @@
+package string_to_integer
+
+// just consider 32-bit, fucking leetcode.com's test cases
+const (
+	MAX int32 = 1<<31 - 1
+	MIN int32 = -1*MAX - 1
+)
+
+func myAtoi(str string) int {
+	if len(str) == 0 {
+		return 0
+	}
+	runes := []rune(str)
+	var ret int32
+	var neg bool
+	i := 0
+	for ; runes[i] == rune(' '); i++ {
+	}
+	if runes[i] == rune('-') || runes[i] == rune('+') {
+		neg = runes[i] == rune('-')
+		i++
+	}
+
+	for ; i < len(runes); i++ {
+		if val, ok := toInt(runes[i]); !ok {
+			break
+		} else {
+			if neg {
+				if -ret < (MIN+val)/10 {
+					return int(MIN)
+				}
+			} else {
+				if ret > (MAX-val)/10 {
+					return int(MAX)
+				}
+			}
+			ret = 10*ret + val
+		}
+	}
+	if neg {
+		return int(-ret)
+	}
+	return int(ret)
+}
+
+func toInt(r rune) (int32, bool) {
+	ret := int32(r - rune('0'))
+	if ret >= 0 && ret <= 9 {
+		return ret, true
+	}
+	return 0, false
+}

string_to_integer/string_to_integer_test.go

@@ -0,0 +1,9 @@
+package string_to_integer
+
+import (
+	"testing"
+)
+
+func TestMyAtoi(t *testing) {
+
+}