Merge pull request #208 from 0xff-dev/master

Add solution and test-cases for problem 415

Author: Cori1109

leetcode/401-500/0415.Add-Strings/README.md

@@ -1,28 +1,32 @@
 # [415.Add Strings][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 two non-negative integers, `num1` and `num2` represented as string, return the sum of `num1` and `num2` as a string.
+
+You must solve the problem without using any built-in library for handling large integers (such as `BigInteger`). You must also not convert the inputs to integers directly.
+
 
 **Example 1:**
 
 ```
-Input: a = "11", b = "1"
-Output: "100"
+Input: num1 = "11", num2 = "123"
+Output: "134"
 ```
 
-## 题意
-> ...
+__Example 2:__
 
-## 题解
-
-### 思路1
-> ...
-Add Strings
-```go
+```
+Input: num1 = "456", num2 = "77"
+Output: "533"
 ```
 
+__Example 3__
+
+```
+Input: num1 = "0", num2 = "0"
+Output: "0"
+```
 
 ## 结语
 

leetcode/401-500/0415.Add-Strings/Solution.go

@@ -1,5 +1,39 @@
 package Solution
 
-func Solution(x bool) bool {
-	return x
+import "bytes"
+
+func Solution(num1 string, num2 string) string {
+	num1Idx, num2Idx := len(num1)-1, len(num2)-1
+
+	buf := bytes.NewBufferString("")
+	cf := uint8(0)
+	for ; num1Idx >= 0 && num2Idx >= 0; num1Idx, num2Idx = num1Idx-1, num2Idx-1 {
+		sum := num1[num1Idx] - '0' + num2[num2Idx] - '0' + cf
+		cf = sum / 10
+		sum %= 10
+		buf.WriteByte(sum + '0')
+	}
+
+	for ; num1Idx >= 0; num1Idx-- {
+		sum := num1[num1Idx] - '0' + cf
+		cf = sum / 10
+		sum %= 10
+		buf.WriteByte(sum + '0')
+	}
+	for ; num2Idx >= 0; num2Idx-- {
+		sum := num2[num2Idx] - '0' + cf
+		cf = sum / 10
+		sum %= 10
+		buf.WriteByte(sum + '0')
+	}
+
+	if cf != 0 {
+		buf.WriteByte(cf + '0')
+	}
+	bs := buf.Bytes()
+	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)
 }

leetcode/401-500/0415.Add-Strings/Solution_test.go

@@ -9,22 +9,22 @@ import (
 func TestSolution(t *testing.T) {
 	//	测试用例
 	cases := []struct {
-		name   string
-		inputs bool
-		expect bool
+		name       string
+		num1, num2 string
+		expect     string
 	}{
-		{"TestCase", true, true},
-		{"TestCase", true, true},
-		{"TestCase", false, false},
+		{"TestCase1", "11", "123", "134"},
+		{"TestCase2", "456", "77", "533"},
+		{"TestCase3", "0", "0", "0"},
 	}
 
 	//	开始测试
 	for i, c := range cases {
 		t.Run(c.name+" "+strconv.Itoa(i), func(t *testing.T) {
-			got := Solution(c.inputs)
+			got := Solution(c.num1, c.num2)
 			if !reflect.DeepEqual(got, c.expect) {
-				t.Fatalf("expected: %v, but got: %v, with inputs: %v",
-					c.expect, got, c.inputs)
+				t.Fatalf("expected: %v, but got: %v, with input-num1: %v, input-num2: %v",
+					c.expect, got, c.num1, c.num2)
 			}
 		})
 	}