Merge pull request 6boris#240 from 0xff-dev/405

Add solution and test-cases for problem 405

Author: 6boris

leetcode/401-500/0405.Convert-a-Number-to-Hexadecimal/README.md

@@ -1,28 +1,25 @@
 # [405.Convert a Number to Hexadecimal][title]
 
-> [!WARNING|style:flat]
-> This question is temporarily unanswered if you have good ideas. Welcome to [Create Pull Request PR](https://github.com/kylesliu/awesome-golang-algorithm)
-
 ## Description
+Given an integer `num`, return a string representing its hexadecimal representation. For negative integers, `two’s complement` method is used.
+
+All the letters in the answer string should be lowercase characters, and there should not be any leading zeros in the answer except for the zero itself.
+
+**Note**: You are not allowed to use any built-in library method to directly solve this problem.
 
 **Example 1:**
 
 ```
-Input: a = "11", b = "1"
-Output: "100"
+Input: num = 26
+Output: "1a"
 ```
 
-## 题意
-> ...
+**Example 2**
 
-## 题解
-
-### 思路1
-> ...
-Convert a Number to Hexadecimal
-```go
 ```
-
+Input: num = -1
+Output: "ffffffff"
+```
 
 ## 结语
 

leetcode/401-500/0405.Convert-a-Number-to-Hexadecimal/Solution.go

@@ -1,5 +1,84 @@
 package Solution
 
-func Solution(x bool) bool {
-	return x
+func Solution(num int) string {
+	n2b := map[int]byte{
+		0: '0', 1: '1', 2: '2', 3: '3', 4: '4', 5: '5', 6: '6', 7: '7',
+		8: '8', 9: '9', 10: 'a', 11: 'b', 12: 'c', 13: 'd', 14: 'e', 15: 'f',
+	}
+	if num >= 0 {
+		bs := make([]byte, 0)
+		for num >= 16 {
+			mod := num % 16
+			num /= 16
+			bs = append(bs, n2b[mod])
+		}
+		bs = append(bs, n2b[num])
+		for s, e := 0, len(bs)-1; s < e; s, e = s+1, e-1 {
+			bs[s], bs[e] = bs[e], bs[s]
+		}
+		return string(bs)
+	}
+	num = -num
+	bs := make([]uint8, 32)
+	bs[0] = 1
+	end := 31
+	for num >= 2 {
+		mod := num % 2
+		bs[end] = uint8(mod)
+		num /= 2
+		end--
+	}
+	bs[end] = uint8(num)
+	cf := uint8(1)
+	for idx := 31; idx > 0; idx-- {
+		bs[idx] ^= uint8(1)
+		bs[idx] += cf
+		cf = bs[idx] / 2
+		bs[idx] %= 2
+	}
+	power := [4]uint8{1, 2, 4, 8}
+	result := make([]byte, 8)
+	bsIdx, idx := 7, 31
+	for idx > 0 {
+		base := uint8(0)
+		for i := 0; i < 4; i++ {
+			base += bs[idx-i] * power[i]
+		}
+		result[bsIdx] = n2b[int(base)]
+		bsIdx--
+		idx -= 4
+	}
+	// ^=1
+	return string(result)
+}
+
+func Solution2(num int) string {
+	maxInt := 2147483647  // 2**31-1
+	minInt := -maxInt - 1 // -2**31
+	compare := 4294967295 // 2**32-1
+	if num > maxInt || num < minInt {
+		return ""
+	}
+	if num == 0 {
+		return "0"
+	}
+	if num < 0 {
+		num = num + 1 + compare
+	}
+	numMap := map[int]byte{
+		0: '0', 1: '1', 2: '2', 3: '3', 4: '4',
+		5: '5', 6: '6', 7: '7', 8: '8', 9: '9',
+		10: 'a', 11: 'b', 12: 'c', 13: 'd', 14: 'e',
+		15: 'f',
+	}
+	res := make([]byte, 0)
+	for num > 0 {
+		remainer := num % 16
+		num = num / 16
+		res = append(res, numMap[remainer])
+	}
+	for s, e := 0, len(res)-1; s < e; s, e = s+1, e-1 {
+		res[s], res[e] = res[e], res[s]
+	}
+	return string(res)
 }

leetcode/401-500/0405.Convert-a-Number-to-Hexadecimal/Solution_test.go

@@ -10,12 +10,14 @@ func TestSolution(t *testing.T) {
 	//	测试用例
 	cases := []struct {
 		name   string
-		inputs bool
-		expect bool
+		inputs int
+		expect string
 	}{
-		{"TestCase", true, true},
-		{"TestCase", true, true},
-		{"TestCase", false, false},
+		{"TestCase1", 26, "1a"},
+		{"TestCase2", -1, "ffffffff"},
+		{"TestCase3", -10, "fffffff6"},
+		{"TestCase4", -23478, "ffffa44a"},
+		{"TestCase5", -2, "fffffffe"},
 	}
 
 	//	开始测试
@@ -26,6 +28,11 @@ func TestSolution(t *testing.T) {
 				t.Fatalf("expected: %v, but got: %v, with inputs: %v",
 					c.expect, got, c.inputs)
 			}
+			got = Solution2(c.inputs)
+			if !reflect.DeepEqual(got, c.expect) {
+				t.Fatalf("expected: %v, but got: %v, with inputs: %v",
+					c.expect, got, c.inputs)
+			}
 		})
 	}
 }