feat: update solutions to lc problems

* No.0415.Add Strings * No.0989.Add to Array-Form of Integer
chenxinxue521 · May 3, 2022 · 832a5a3 · 832a5a3
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diff --git a/README.md b/README.md
@@ -39,6 +39,7 @@
 -   [找到需要补充粉笔的学生编号](/solution/1800-1899/1894.Find%20the%20Student%20that%20Will%20Replace%20the%20Chalk/README.md) - 二分查找
 -   [可移除字符的最大数目](/solution/1800-1899/1898.Maximum%20Number%20of%20Removable%20Characters/README.md) - 二分查找
 -   [排序数组](/solution/0900-0999/0912.Sort%20an%20Array/README.md) - 快速排序、归并排序
+-   [字符串相加](/solution/0400-0499/0415.Add%20Strings/README.md) - 高精度加法
 <!-- 排序算法、待补充 -->
 
 ### 2. 搜索

diff --git a/README_EN.md b/README_EN.md
@@ -38,6 +38,7 @@ Complete solutions to [LeetCode](https://leetcode.com/problemset/all/), [LCOF](h
 -   [Find the Student that Will Replace the Chalk](/solution/1800-1899/1894.Find%20the%20Student%20that%20Will%20Replace%20the%20Chalk/README_EN.md) - Binary search
 -   [Maximum Number of Removable Characters](/solution/1800-1899/1898.Maximum%20Number%20of%20Removable%20Characters/README_EN.md) - Binary search
 -   [Sort an Array](/solution/0900-0999/0912.Sort%20an%20Array/README_EN.md) - Quick Sort, Merge Sort
+-   [Add Strings](/solution/0400-0499/0415.Add%20Strings/README_EN.md) - Addition of large numbers
 
 ### 2. Search
 

diff --git a/solution/0400-0499/0415.Add Strings/README.md b/solution/0400-0499/0415.Add Strings/README.md
@@ -58,13 +58,12 @@
 ```python
 class Solution:
     def addStrings(self, num1: str, num2: str) -> str:
+        i, j, carry = len(num1) - 1, len(num2) - 1, 0
         ans = []
-        i, j = len(num1) - 1, len(num2) - 1
-        carry = 0
         while i >= 0 or j >= 0 or carry:
             carry += (0 if i < 0 else int(num1[i])) + (0 if j < 0 else int(num2[j]))
-            ans.append(str(carry % 10))
-            carry //= 10
+            carry, v = divmod(carry, 10)
+            ans.append(str(v))
             i, j = i - 1, j - 1
         return ''.join(ans[::-1])
 ```
@@ -76,11 +75,10 @@ class Solution:
 ```java
 class Solution {
     public String addStrings(String num1, String num2) {
-        int i = num1.length() - 1, j = num2.length() - 1;
-        int carry = 0;
         StringBuilder ans = new StringBuilder();
-        while (i >= 0 || j >= 0 || carry > 0) {
-            carry += (i < 0 ? 0 : num1.charAt(i--) - '0') + (j < 0 ? 0 : num2.charAt(j--) - '0');
+        int i = num1.length() - 1, j = num2.length() - 1, carry = 0;
+        for (; i >= 0 || j >= 0 || carry > 0; --i, --j) {
+            carry += (i < 0 ? 0 : num1.charAt(i) - '0') + (j < 0 ? 0 : num2.charAt(j) - '0');
             ans.append(carry % 10);
             carry /= 10;
         }
@@ -99,18 +97,14 @@ class Solution {
  */
 var addStrings = function (num1, num2) {
     let ans = [];
-    for (
-        let i = num1.length - 1, j = num2.length - 1, sum = 0;
-        i >= 0 || j >= 0 || sum > 0;
-        i--, j--
-    ) {
-        const a = i >= 0 ? parseInt(num1.charAt(i), 10) : 0;
-        const b = j >= 0 ? parseInt(num2.charAt(j), 10) : 0;
-        sum += a + b;
-        ans.unshift(sum % 10);
-        sum = Math.floor(sum / 10);
+    let [i, j, carry] = [num1.length - 1, num2.length - 1, 0];
+    for (; i >= 0 || j >= 0 || carry; --i, --j) {
+        carry += i < 0 ? 0 : parseInt(num1.charAt(i), 10);
+        carry += j < 0 ? 0 : parseInt(num2.charAt(j), 10);
+        ans.push(carry % 10);
+        carry = Math.floor(carry / 10);
     }
-    return ans.join('');
+    return ans.reverse().join('');
 };
 ```
 
@@ -120,12 +114,11 @@ var addStrings = function (num1, num2) {
 class Solution {
 public:
     string addStrings(string num1, string num2) {
-        int i = num1.size() - 1, j = num2.size() - 1;
-        int carry = 0;
         string ans;
-        while (i >= 0 || j >= 0 || carry)
+        int i = num1.size() - 1, j = num2.size() - 1, carry = 0;
+        for (; i >= 0 || j >= 0 || carry; --i, --j)
         {
-            carry += (i < 0 ? 0 : num1[i--] - '0') + (j < 0 ? 0 : num2[j--] - '0');
+            carry += (i < 0 ? 0 : num1[i] - '0') + (j < 0 ? 0 : num2[j] - '0');
             ans += to_string(carry % 10);
             carry /= 10;
         }
@@ -139,9 +132,9 @@ public:
 
 ```go
 func addStrings(num1 string, num2 string) string {
-	carry := 0
 	ans := ""
-	for i, j := len(num1)-1, len(num2)-1; i >= 0 || j >= 0 || carry != 0; i, j = i-1, j-1 {
+	i, j, carry := len(num1)-1, len(num2)-1, 0
+	for ; i >= 0 || j >= 0 || carry != 0; i, j = i-1, j-1 {
 		if i >= 0 {
 			carry += int(num1[i] - '0')
 		}

diff --git a/solution/0400-0499/0415.Add Strings/README_EN.md b/solution/0400-0499/0415.Add Strings/README_EN.md
@@ -48,13 +48,12 @@
 ```python
 class Solution:
     def addStrings(self, num1: str, num2: str) -> str:
+        i, j, carry = len(num1) - 1, len(num2) - 1, 0
         ans = []
-        i, j = len(num1) - 1, len(num2) - 1
-        carry = 0
         while i >= 0 or j >= 0 or carry:
             carry += (0 if i < 0 else int(num1[i])) + (0 if j < 0 else int(num2[j]))
-            ans.append(str(carry % 10))
-            carry //= 10
+            carry, v = divmod(carry, 10)
+            ans.append(str(v))
             i, j = i - 1, j - 1
         return ''.join(ans[::-1])
 ```
@@ -64,11 +63,10 @@ class Solution:
 ```java
 class Solution {
     public String addStrings(String num1, String num2) {
-        int i = num1.length() - 1, j = num2.length() - 1;
-        int carry = 0;
         StringBuilder ans = new StringBuilder();
-        while (i >= 0 || j >= 0 || carry > 0) {
-            carry += (i < 0 ? 0 : num1.charAt(i--) - '0') + (j < 0 ? 0 : num2.charAt(j--) - '0');
+        int i = num1.length() - 1, j = num2.length() - 1, carry = 0;
+        for (; i >= 0 || j >= 0 || carry > 0; --i, --j) {
+            carry += (i < 0 ? 0 : num1.charAt(i) - '0') + (j < 0 ? 0 : num2.charAt(j) - '0');
             ans.append(carry % 10);
             carry /= 10;
         }
@@ -87,18 +85,14 @@ class Solution {
  */
 var addStrings = function (num1, num2) {
     let ans = [];
-    for (
-        let i = num1.length - 1, j = num2.length - 1, sum = 0;
-        i >= 0 || j >= 0 || sum > 0;
-        i--, j--
-    ) {
-        const a = i >= 0 ? parseInt(num1.charAt(i), 10) : 0;
-        const b = j >= 0 ? parseInt(num2.charAt(j), 10) : 0;
-        sum += a + b;
-        ans.unshift(sum % 10);
-        sum = Math.floor(sum / 10);
+    let [i, j, carry] = [num1.length - 1, num2.length - 1, 0];
+    for (; i >= 0 || j >= 0 || carry; --i, --j) {
+        carry += i < 0 ? 0 : parseInt(num1.charAt(i), 10);
+        carry += j < 0 ? 0 : parseInt(num2.charAt(j), 10);
+        ans.push(carry % 10);
+        carry = Math.floor(carry / 10);
     }
-    return ans.join('');
+    return ans.reverse().join('');
 };
 ```
 
@@ -108,12 +102,11 @@ var addStrings = function (num1, num2) {
 class Solution {
 public:
     string addStrings(string num1, string num2) {
-        int i = num1.size() - 1, j = num2.size() - 1;
-        int carry = 0;
         string ans;
-        while (i >= 0 || j >= 0 || carry)
+        int i = num1.size() - 1, j = num2.size() - 1, carry = 0;
+        for (; i >= 0 || j >= 0 || carry; --i, --j)
         {
-            carry += (i < 0 ? 0 : num1[i--] - '0') + (j < 0 ? 0 : num2[j--] - '0');
+            carry += (i < 0 ? 0 : num1[i] - '0') + (j < 0 ? 0 : num2[j] - '0');
             ans += to_string(carry % 10);
             carry /= 10;
         }
@@ -127,9 +120,9 @@ public:
 
 ```go
 func addStrings(num1 string, num2 string) string {
-	carry := 0
 	ans := ""
-	for i, j := len(num1)-1, len(num2)-1; i >= 0 || j >= 0 || carry != 0; i, j = i-1, j-1 {
+	i, j, carry := len(num1)-1, len(num2)-1, 0
+	for ; i >= 0 || j >= 0 || carry != 0; i, j = i-1, j-1 {
 		if i >= 0 {
 			carry += int(num1[i] - '0')
 		}

diff --git a/solution/0400-0499/0415.Add Strings/Solution.cpp b/solution/0400-0499/0415.Add Strings/Solution.cpp
@@ -1,12 +1,11 @@
 class Solution {
 public:
     string addStrings(string num1, string num2) {
-        int i = num1.size() - 1, j = num2.size() - 1;
-        int carry = 0;
         string ans;
-        while (i >= 0 || j >= 0 || carry)
+        int i = num1.size() - 1, j = num2.size() - 1, carry = 0;
+        for (; i >= 0 || j >= 0 || carry; --i, --j)
         {
-            carry += (i < 0 ? 0 : num1[i--] - '0') + (j < 0 ? 0 : num2[j--] - '0');
+            carry += (i < 0 ? 0 : num1[i] - '0') + (j < 0 ? 0 : num2[j] - '0');
             ans += to_string(carry % 10);
             carry /= 10;
         }

diff --git a/solution/0400-0499/0415.Add Strings/Solution.go b/solution/0400-0499/0415.Add Strings/Solution.go
@@ -1,7 +1,7 @@
 func addStrings(num1 string, num2 string) string {
-	carry := 0
 	ans := ""
-	for i, j := len(num1)-1, len(num2)-1; i >= 0 || j >= 0 || carry != 0; i, j = i-1, j-1 {
+	i, j, carry := len(num1)-1, len(num2)-1, 0
+	for ; i >= 0 || j >= 0 || carry != 0; i, j = i-1, j-1 {
 		if i >= 0 {
 			carry += int(num1[i] - '0')
 		}

diff --git a/solution/0400-0499/0415.Add Strings/Solution.java b/solution/0400-0499/0415.Add Strings/Solution.java
@@ -1,10 +1,9 @@
 class Solution {
     public String addStrings(String num1, String num2) {
-        int i = num1.length() - 1, j = num2.length() - 1;
-        int carry = 0;
         StringBuilder ans = new StringBuilder();
-        while (i >= 0 || j >= 0 || carry > 0) {
-            carry += (i < 0 ? 0 : num1.charAt(i--) - '0') + (j < 0 ? 0 : num2.charAt(j--) - '0');
+        int i = num1.length() - 1, j = num2.length() - 1, carry = 0;
+        for (; i >= 0 || j >= 0 || carry > 0; --i, --j) {
+            carry += (i < 0 ? 0 : num1.charAt(i) - '0') + (j < 0 ? 0 : num2.charAt(j) - '0');
             ans.append(carry % 10);
             carry /= 10;
         }

diff --git a/solution/0400-0499/0415.Add Strings/Solution.js b/solution/0400-0499/0415.Add Strings/Solution.js
@@ -5,16 +5,12 @@
  */
 var addStrings = function (num1, num2) {
     let ans = [];
-    for (
-        let i = num1.length - 1, j = num2.length - 1, sum = 0;
-        i >= 0 || j >= 0 || sum > 0;
-        i--, j--
-    ) {
-        const a = i >= 0 ? parseInt(num1.charAt(i), 10) : 0;
-        const b = j >= 0 ? parseInt(num2.charAt(j), 10) : 0;
-        sum += a + b;
-        ans.unshift(sum % 10);
-        sum = Math.floor(sum / 10);
+    let [i, j, carry] = [num1.length - 1, num2.length - 1, 0];
+    for (; i >= 0 || j >= 0 || carry; --i, --j) {
+        carry += i < 0 ? 0 : parseInt(num1.charAt(i), 10);
+        carry += j < 0 ? 0 : parseInt(num2.charAt(j), 10);
+        ans.push(carry % 10);
+        carry = Math.floor(carry / 10);
     }
-    return ans.join('');
+    return ans.reverse().join('');
 };
diff --git a/solution/0400-0499/0415.Add Strings/Solution.py b/solution/0400-0499/0415.Add Strings/Solution.py
@@ -1,11 +1,10 @@
 class Solution:
     def addStrings(self, num1: str, num2: str) -> str:
+        i, j, carry = len(num1) - 1, len(num2) - 1, 0
         ans = []
-        i, j = len(num1) - 1, len(num2) - 1
-        carry = 0
         while i >= 0 or j >= 0 or carry:
             carry += (0 if i < 0 else int(num1[i])) + (0 if j < 0 else int(num2[j]))
-            ans.append(str(carry % 10))
-            carry //= 10
+            carry, v = divmod(carry, 10)
+            ans.append(str(v))
             i, j = i - 1, j - 1
         return ''.join(ans[::-1])
diff --git a/solution/0900-0999/0989.Add to Array-Form of Integer/README.md b/solution/0900-0999/0989.Add to Array-Form of Integer/README.md
@@ -58,7 +58,7 @@
 
 <!-- 这里可写通用的实现逻辑 -->
 
-数组从尾到头遍历，分别与 `K` 中的每一位相加，进位保存在 `carry` 中，不进位和则添加到结果列表中。最后逆序结果列表即可。
+数组从尾到头遍历，分别与 `k` 中的每一位相加，进位保存在 `carry` 中，不进位和则添加到结果列表中。最后逆序结果列表即可。
 
 <!-- tabs:start -->
 
@@ -68,16 +68,16 @@
 
 ```python
 class Solution:
-    def addToArrayForm(self, A: List[int], K: int) -> List[int]:
-        n = len(A) - 1
-        carry, res = 0, []
-        while n >= 0 or K != 0 or carry != 0:
-            carry += (0 if n < 0 else A[n]) + (K % 10)
-            res.append(carry % 10)
-            K //= 10
-            carry //= 10
-            n -= 1
-        return res[::-1]
+    def addToArrayForm(self, num: List[int], k: int) -> List[int]:
+        i, carry = len(num) - 1, 0
+        ans = []
+        while i >= 0 or k or carry:
+            carry += (0 if i < 0 else num[i]) + (k % 10)
+            carry, v = divmod(carry, 10)
+            ans.append(v)
+            k //= 10
+            i -= 1
+        return ans[::-1]
 ```
 
 ### **Java**
@@ -86,19 +86,16 @@ class Solution:
 
 ```java
 class Solution {
-    public List<Integer> addToArrayForm(int[] A, int K) {
-        int n = A.length - 1;
-        List<Integer> res = new ArrayList<>();
-        int carry = 0;
-        while (n >= 0 || K != 0 || carry != 0) {
-            carry += (n < 0 ? 0 : A[n]) + (K % 10);
-            res.add(carry % 10);
-            K /= 10;
+    public List<Integer> addToArrayForm(int[] num, int k) {
+        int i = num.length - 1, carry = 0;
+        LinkedList<Integer> ans = new LinkedList<>();
+        while (i >= 0 || k > 0 || carry > 0) {
+            carry += (i < 0 ? 0 : num[i--]) + k % 10;
+            ans.addFirst(carry % 10);
             carry /= 10;
-            --n;
+            k /= 10;
         }
-        Collections.reverse(res);
-        return res;
+        return ans;
     }
 }
 ```
@@ -161,6 +158,49 @@ impl Solution {
 }
 ```
 
+### **C++**
+
+```cpp
+class Solution {
+public:
+    vector<int> addToArrayForm(vector<int>& num, int k) {
+        int i = num.size() - 1, carry = 0;
+        vector<int> ans;
+        for (; i >= 0 || k || carry; --i)
+        {
+            carry += (i < 0 ? 0 : num[i]) + k % 10;
+            ans.push_back(carry % 10);
+            carry /= 10;
+            k /= 10;
+        }
+        reverse(ans.begin(), ans.end());
+        return ans;
+    }
+};
+```
+
+### **Go**
+
+```go
+func addToArrayForm(num []int, k int) []int {
+	i, carry := len(num)-1, 0
+	ans := []int{}
+	for ; i >= 0 || k > 0 || carry > 0; i-- {
+		if i >= 0 {
+			carry += num[i]
+		}
+		carry += k % 10
+		ans = append(ans, carry%10)
+		carry /= 10
+		k /= 10
+	}
+	for i, j := 0, len(ans)-1; i < j; i, j = i+1, j-1 {
+		ans[i], ans[j] = ans[j], ans[i]
+	}
+	return ans
+}
+```
+
 ### **...**
 
 ```