67 finish

Author: aQua

Algorithms/0067.add-binary/README.md

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+# [67. Add Binary](https://leetcode.com/problems/add-binary/)
+
+## 题目
+Given two binary strings, return their sum (also a binary string).
+
+```
+For example,
+a = "11"
+b = "1"
+Return "100".
+```
+## 解题思路
+
+见程序注释

Algorithms/0067.add-binary/add-binary.go

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+package Problem0067
+
+func addBinary(a string, b string) string {
+	if len(a) < len(b) {
+		a, b = b, a
+	}
+	l := len(a)
+
+	isA := trans(a, l)
+	isB := trans(b, l)
+
+	return makeString(add(isA, isB))
+}
+
+func trans(s string, l int) []int {
+	res := make([]int, l)
+	ls := len(s)
+	for i, b := range s {
+		res[l-ls+i] = int(b - '0')
+	}
+
+	return res
+}
+
+func add(a, b []int) []int {
+	l := len(a) + 1
+	res := make([]int, l)
+	for i := l - 1; i >= 1; i-- {
+		temp := res[i] + a[i-1] + b[i-1]
+		res[i] = temp % 2
+		res[i-1] = temp / 2
+	}
+
+	i := 0
+
+	// i < l-1 而不是 l 的原因是
+	// "" + "" == "0"
+	// 需要保留最后一个 '0'
+	for i < l-1 && res[i] == 0 {
+		i++
+	}
+
+	return res[i:]
+}
+
+func makeString(nums []int) string {
+	bytes := make([]byte, len(nums))
+	for i := range bytes {
+		bytes[i] = byte(nums[i]) + '0'
+	}
+
+	return string(bytes)
+}

Algorithms/0067.add-binary/add-binary_test.go

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+package Problem0067
+
+import (
+	"fmt"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+type question struct {
+	para
+	ans
+}
+
+// para 是参数
+type para struct {
+	a string
+	b string
+}
+
+// ans 是答案
+type ans struct {
+	one string
+}
+
+func Test_Problem0067(t *testing.T) {
+	ast := assert.New(t)
+
+	qs := []question{
+
+		question{
+			para{
+				"11",
+				"1",
+			},
+			ans{
+				"100",
+			},
+		},
+
+		question{
+			para{
+				"001",
+				"000",
+			},
+			ans{
+				"1",
+			},
+		},
+
+		question{
+			para{
+				"",
+				"",
+			},
+			ans{
+				"0",
+			},
+		},
+
+		question{
+			para{
+				"",
+				"1",
+			},
+			ans{
+				"1",
+			},
+		},
+		// 如需多个测试，可以复制上方元素。
+	}
+
+	for _, q := range qs {
+		a, p := q.ans, q.para
+		fmt.Printf("~~%v~~\n", p)
+
+		ast.Equal(a.one, addBinary(p.a, p.b), "输入:%v", p)
+	}
+}