diff --git a/problems/0018.四数之和.md b/problems/0018.四数之和.md
index 0caf12be..4a8fa947 100644
--- a/problems/0018.四数之和.md
+++ b/problems/0018.四数之和.md
@@ -201,6 +201,54 @@ class Solution(object):
 ```
 
 Go：
+```go
+func fourSum(nums []int, target int) [][]int {
+	if len(nums) < 4 {
+		return nil
+	}
+	sort.Ints(nums)
+	var res [][]int
+	for i := 0; i < len(nums)-3; i++ {
+		n1 := nums[i]
+		// if n1 > target { // 不能这样写,因为可能是负数
+		// 	break
+		// }
+		if i > 0 && n1 == nums[i-1] {
+			continue
+		}
+		for j := i + 1; j < len(nums)-2; j++ {
+			n2 := nums[j]
+			if j > i+1 && n2 == nums[j-1] {
+				continue
+			}
+			l := j + 1
+			r := len(nums) - 1
+			for l < r {
+				n3 := nums[l]
+				n4 := nums[r]
+				sum := n1 + n2 + n3 + n4
+				if sum < target {
+					l++
+				} else if sum > target {
+					r--
+				} else {
+					res = append(res, []int{n1, n2, n3, n4})
+					for l < r && n3 == nums[l+1] { // 去重
+						l++
+					}
+					for l < r && n4 == nums[r-1] { // 去重
+						r--
+					}
+					// 找到答案时,双指针同时靠近
+					r--
+					l++
+				}
+			}
+		}
+	}
+	return res
+}
+```
 
 javaScript: 
 
diff --git a/problems/0100.相同的树.md b/problems/0100.相同的树.md
index b536ffe3..c40f79fd 100644
--- a/problems/0100.相同的树.md
+++ b/problems/0100.相同的树.md
@@ -172,6 +172,22 @@ public:
 
 Java：
 
+```java
+class Solution {
+    public boolean isSameTree(TreeNode p, TreeNode q) {
+        if (p == null && q == null) {
+            return true;
+        } else if (q == null || p == null) {
+            return false;
+        } else if (q.val != p.val) {
+            return false;
+        } else {
+            return isSameTree(q.left, p.left) && isSameTree(q.right, p.right);
+        }
+    }
+}
+
+```
 Python：
 
 Go：
diff --git a/problems/1002.查找常用字符.md b/problems/1002.查找常用字符.md
index 875340c4..e3014d00 100644
--- a/problems/1002.查找常用字符.md
+++ b/problems/1002.查找常用字符.md
@@ -169,6 +169,46 @@ class Solution {
     }
 }
 ```
+javaScript
+```js
+var commonChars = function (words) {
+	let res = []
+	let size = 26
+	let firstHash = new Array(size)
+	for (let i = 0; i < size; i++) { // 初始化 hash 数组
+		firstHash[i] = 0
+	}
+
+	let a = "a".charCodeAt()
+	let firstWord = words[0]
+	for (let i = 0; i < firstWord.length; i++) { // 第 0 个单词的统计
+		let idx = firstWord[i].charCodeAt()
+		firstHash[idx - a] += 1
+	}
+
+	for (let i = 1; i < words.length; i++) { // 1-n 个单词统计
+		let otherHash = new Array(size)
+		for (let i = 0; i < size; i++) { // 初始化 hash 数组
+			otherHash[i] = 0
+		}
+
+		for (let j = 0; j < words[i].length; j++) {
+			let idx = words[i][j].charCodeAt()
+			otherHash[idx - a] += 1
+		}
+		for (let i = 0; i < size; i++) {
+			firstHash[i] = Math.min(firstHash[i], otherHash[i])
+		}
+	}
+	for (let i = 0; i < size; i++) {
+		while (firstHash[i] > 0) {
+			res.push(String.fromCharCode(i + a))
+			firstHash[i]--
+		}
+	}
+	return res
+};
+```
 
 -----------------------
 * 作者微信：[程序员Carl](https://mp.weixin.qq.com/s/b66DFkOp8OOxdZC_xLZxfw)