add new solutions

solutions/0/q43/solution.go

@@ -0,0 +1,49 @@
+package q43
+
+import "slices"
+
+func multiply(num1, num2 string) string {
+	if num1 == "0" || num2 == "0" {
+		return "0"
+	}
+
+	l1, l2 := len(num1), len(num2)
+	res := make([]byte, l1+l2)
+
+	// Calculation
+	for i1 := range l1 {
+		n1 := num1[l1-1-i1] - '0'
+		if n1 == 0 {
+			continue
+		}
+		for i2 := range l2 {
+			n2 := num2[l2-1-i2] - '0'
+			j := i1 + i2
+			res[j] += n1 * n2
+			if res[j] > 9 {
+				res[j+1] += res[j] / 10
+				res[j] = res[j] % 10
+			}
+		}
+		for i := l2 + i1; res[i] > 9; i++ {
+			res[i+1] += res[i] / 10
+			res[i] = res[i] % 10
+		}
+	}
+
+	// Post process
+	for i := len(res) - 1; i >= 0; i-- {
+		if res[i] > 0 {
+			res = res[:i+1]
+			break
+		}
+	}
+
+	slices.Reverse(res)
+	for i := range res {
+		res[i] = res[i] + '0'
+	}
+	return string(res)
+}
+
+var _ = multiply

solutions/0/q68/solution.go

@@ -0,0 +1,63 @@
+package q68
+
+var (
+	emptyLine = make([]byte, 100)
+	buf       = make([]byte, 100)
+)
+
+func init() {
+	for i := range emptyLine {
+		emptyLine[i] = ' '
+	}
+}
+
+func emitLine(line []byte, words []string, justifyLeft bool) string {
+	spaces := len(line)
+	for i := range words {
+		spaces -= len(words[i])
+	}
+	lenSep := spaces / max(len(words)-1, 1)
+	leftover := spaces % max(len(words)-1, 1)
+
+	offset := len(words[0])
+	copy(line, words[0])
+	for i := 1; i < len(words); i++ {
+		var spaces = 1
+		if !justifyLeft {
+			spaces = lenSep
+			if i <= leftover {
+				spaces++
+			}
+		}
+		offset += spaces
+		copy(line[offset:], words[i])
+		offset += len(words[i])
+	}
+	return string(line)
+}
+
+func fullJustify(words []string, maxWidth int) []string {
+	ret := []string{}
+	line := buf[:maxWidth]
+	copy(line, emptyLine)
+
+	i := 0
+	lineLen := len(words[0])
+	for j := 1; j < len(words); j++ {
+		if lineLen+1+len(words[j]) <= maxWidth {
+			lineLen += 1 + len(words[j])
+			continue
+		}
+
+		ret = append(ret, emitLine(line, words[i:j], false))
+		copy(line, emptyLine)
+
+		i = j
+		lineLen = len(words[j])
+	}
+
+	// Last line
+	return append(ret, emitLine(line, words[i:], true))
+}
+
+var _ = fullJustify

solutions/0/q8/solution.go

@@ -0,0 +1,56 @@
+package q8
+
+const (
+	MIN = -(1 << 31)
+	MAX = 1<<31 - 1
+)
+
+func myAtoi(s string) int {
+	sign := 0
+	num := 0
+
+Loop:
+	for i := range len(s) {
+		c := s[i]
+
+		switch c {
+		case '-':
+			if sign != 0 {
+				break Loop
+			}
+			sign = -1
+
+		case '+':
+			if sign != 0 {
+				break Loop
+			}
+			sign = 1
+
+		case ' ':
+			if sign != 0 {
+				break Loop
+			}
+
+		default:
+			if c < '0' || c > '9' {
+				break Loop
+			}
+			if sign == 0 {
+				sign = 1
+			}
+			num = num*10 + int(c-'0')
+			if sign*num < MIN {
+				num = -MIN
+				break Loop
+			}
+			if sign*num > MAX {
+				num = MAX
+				break Loop
+			}
+		}
+	}
+
+	return sign * num
+}
+
+var _ = myAtoi