feat: update solutions to leetcode problems: No.0007, No.0389

Author: yanglbme

solution/0000-0099/0007.Reverse Integer/README.md

@@ -49,7 +49,6 @@
 	<li><code>-2<sup>31</sup> <= x <= 2<sup>31</sup> - 1</code></li>
 </ul>
 
-
 ## 解法
 
 <!-- 这里可写通用的实现逻辑 -->
@@ -104,6 +103,23 @@ public:
 };
 ```
 
+### **JavaScript**
+
+```js
+/**
+ * @param {number} x
+ * @return {number}
+ */
+var reverse = function (x) {
+  let res = 0;
+  while (x) {
+    res = res * 10 + (x % 10);
+    x = ~~(x / 10);
+  }
+  return res < Math.pow(-2, 31) || res > Math.pow(2, 31) - 1 ? 0 : res;
+};
+```
+
 ### **...**
 
 ```

solution/0000-0099/0007.Reverse Integer/README_EN.md

@@ -29,7 +29,6 @@
 	<li><code>-2<sup>31</sup> &lt;= x &lt;= 2<sup>31</sup> - 1</code></li>
 </ul>
 
-
 ## Solutions
 
 <!-- tabs:start -->
@@ -75,6 +74,23 @@ public:
 };
 ```
 
+### **JavaScript**
+
+```js
+/**
+ * @param {number} x
+ * @return {number}
+ */
+var reverse = function (x) {
+  let res = 0;
+  while (x) {
+    res = res * 10 + (x % 10);
+    x = ~~(x / 10);
+  }
+  return res < Math.pow(-2, 31) || res > Math.pow(2, 31) - 1 ? 0 : res;
+};
+```
+
 ### **...**
 
 ```

solution/0000-0099/0007.Reverse Integer/Solution.js

@@ -2,51 +2,11 @@
  * @param {number} x
  * @return {number}
  */
-
-/**
- *  Author: mcnwork2018
- */
-
 var reverse = function (x) {
-  let min = -Math.pow(2, 31),
-    max = Math.pow(2, 31) - 1;
-  let rev = 0;
-  while (x != 0) {
-    let pop = x % 10;
-    x = (x - pop) / 10;
-    if (rev > max / 10 || (rev == max / 10 && pop > 7)) return 0;
-    if (rev < min / 10 || (rev == min / 10 && pop < -8)) return 0;
-    rev = rev * 10 + pop;
-  }
-  return rev;
-};
-
-/**
- *  Author: rookie
- */
-
-var reverse = function (x) {
-  const s = x + "";
-  let i = 0;
-  let sign = 1;
-  if (s[i] == "-") {
-    i++;
-    sign = -1;
-  }
-  if (s[i] == "+") {
-    i++;
-  }
-  let num = 0;
-  for (let j = s.length - 1; j >= i; j--) {
-    num = num * 10 + parseInt(s[j]);
-  }
-  num *= sign;
-  let max = 2;
-  for (let n = 0; n < 30; n++) {
-    max *= 2;
-  }
-  if (num > max || num < -max) {
-    return 0;
+  let res = 0;
+  while (x) {
+    res = res * 10 + (x % 10);
+    x = ~~(x / 10);
   }
-  return num;
+  return res < Math.pow(-2, 31) || res > Math.pow(2, 31) - 1 ? 0 : res;
 };

solution/0300-0399/0389.Find the Difference/README.md

@@ -49,27 +49,53 @@
 	<li><code>s</code> 和 <code>t</code> 只包含小写字母</li>
 </ul>
 
-
 ## 解法
 
 <!-- 这里可写通用的实现逻辑 -->
 
+计数器实现。
+
 <!-- tabs:start -->
 
 ### **Python3**
 
 <!-- 这里可写当前语言的特殊实现逻辑 -->
 
 ```python
-
+class Solution:
+    def findTheDifference(self, s: str, t: str) -> str:
+        counter = collections.Counter()
+        for c in s:
+            counter[c] += 1
+        for c in t:
+            if counter[c] <= 0:
+                return c
+            counter[c] -= 1
+        return None
 ```
 
 ### **Java**
 
 <!-- 这里可写当前语言的特殊实现逻辑 -->
 
 ```java
-
+class Solution {
+    public char findTheDifference(String s, String t) {
+        int[] counter = new int[26];
+        for (int i = 0; i < s.length(); ++i) {
+            int index = s.charAt(i) - 'a';
+            ++counter[index];
+        }
+        for (int i = 0; i < t.length(); ++i) {
+            int index = t.charAt(i) - 'a';
+            if (counter[index] <= 0) {
+                return t.charAt(i);
+            }
+            --counter[index];
+        }
+        return ' ';
+    }
+}
 ```
 
 ### **...**

solution/0300-0399/0389.Find the Difference/README_EN.md

@@ -49,21 +49,45 @@
 	<li><code>s</code> and <code>t</code> consist of lower-case English letters.</li>
 </ul>
 
-
 ## Solutions
 
 <!-- tabs:start -->
 
 ### **Python3**
 
 ```python
-
+class Solution:
+    def findTheDifference(self, s: str, t: str) -> str:
+        counter = collections.Counter()
+        for c in s:
+            counter[c] += 1
+        for c in t:
+            if counter[c] <= 0:
+                return c
+            counter[c] -= 1
+        return None
 ```
 
 ### **Java**
 
 ```java
-
+class Solution {
+    public char findTheDifference(String s, String t) {
+        int[] counter = new int[26];
+        for (int i = 0; i < s.length(); ++i) {
+            int index = s.charAt(i) - 'a';
+            ++counter[index];
+        }
+        for (int i = 0; i < t.length(); ++i) {
+            int index = t.charAt(i) - 'a';
+            if (counter[index] <= 0) {
+                return t.charAt(i);
+            }
+            --counter[index];
+        }
+        return ' ';
+    }
+}
 ```
 
 ### **...**

solution/0300-0399/0389.Find the Difference/Solution.java

@@ -0,0 +1,17 @@
+class Solution {
+    public char findTheDifference(String s, String t) {
+        int[] counter = new int[26];
+        for (int i = 0; i < s.length(); ++i) {
+            int index = s.charAt(i) - 'a';
+            ++counter[index];
+        }
+        for (int i = 0; i < t.length(); ++i) {
+            int index = t.charAt(i) - 'a';
+            if (counter[index] <= 0) {
+                return t.charAt(i);
+            }
+            --counter[index];
+        }
+        return ' ';
+    }
+}

solution/0300-0399/0389.Find the Difference/Solution.py

@@ -0,0 +1,10 @@
+class Solution:
+    def findTheDifference(self, s: str, t: str) -> str:
+        counter = collections.Counter()
+        for c in s:
+            counter[c] += 1
+        for c in t:
+            if counter[c] <= 0:
+                return c
+            counter[c] -= 1
+        return None