Merge branch 'youngyangyang04:master' into dev

problems/0015.三数之和.md

@@ -336,6 +336,23 @@ var threeSum = function(nums) {
 ```
 
 
+ruby:
+```ruby
+def is_valid(strs)
+    symbol_map = {')' => '(', '}' => '{', ']' => '['}
+    stack = []
+    strs.size.times {|i|
+        c = strs[i]
+        if symbol_map.has_key?(c)
+            top_e = stack.shift
+            return false if symbol_map[c] != top_e
+        else
+            stack.unshift(c)
+        end
+    }
+    stack.empty?
+end
+```
 
 -----------------------
 * 作者微信：[程序员Carl](https://mp.weixin.qq.com/s/b66DFkOp8OOxdZC_xLZxfw)

problems/0027.移除元素.md

@@ -186,6 +186,20 @@ var removeElement = (nums, val) => {
 };
 ```
 
+Ruby:
+```ruby
+def remove_element(nums, val)
+    i = 0
+    nums.each_index do |j| 
+        if nums[j] != val
+            nums[i] = nums[j]
+            i+=1
+        end
+    end
+    i
+end
+```
+
 -----------------------
 * 作者微信：[程序员Carl](https://mp.weixin.qq.com/s/b66DFkOp8OOxdZC_xLZxfw)
 * B站视频：[代码随想录](https://space.bilibili.com/525438321)

problems/0096.不同的二叉搜索树.md

@@ -186,7 +186,16 @@ class Solution {
 ```
 
 Python：
-
+```python
+class Solution:
+    def numTrees(self, n: int) -> int:
+        dp = [0] * (n + 1)
+        dp[0], dp[1] = 1, 1
+        for i in range(2, n + 1):
+            for j in range(1, i + 1):
+                dp[i] += dp[j - 1] * dp[i - j]
+        return dp[-1]
+```
 
 Go：
 ```Go

problems/0349.两个数组的交集.md

@@ -132,6 +132,23 @@ class Solution:
 
 
 Go：
+```go
+func intersection(nums1 []int, nums2 []int) []int {
+    m := make(map[int]int)
+    for _, v := range nums1 {
+        m[v] = 1
+    }
+    var res []int
+    // 利用count>0，实现重复值只拿一次放入返回结果中
+    for _, v := range nums2 {
+        if count, ok := m[v]; ok && count > 0 {
+            res = append(res, v)
+            m[v]--
+        }
+    }
+    return res
+}
+```
 
 javaScript: