diff --git a/problems/0001.两数之和.md b/problems/0001.两数之和.md
index 31a808b0..5be94996 100644
--- a/problems/0001.两数之和.md
+++ b/problems/0001.两数之和.md
@@ -187,7 +187,23 @@ var twoSum = function (nums, target) {
 };
 ```
 
+php
 
+```php
+function twoSum(array $nums, int $target): array
+{
+    for ($i = 0; $i < count($nums);$i++) {
+        // 计算剩下的数
+        $residue = $target - $nums[$i];
+        // 匹配的index，有则返回index， 无则返回false
+        $match_index = array_search($residue, $nums);
+        if ($match_index !== false && $match_index != $i) {
+            return array($i, $match_index);
+        }
+    }
+    return [];
+}
+```
 
 
 -----------------------
diff --git a/problems/0015.三数之和.md b/problems/0015.三数之和.md
index 5b77a170..36abb58c 100644
--- a/problems/0015.三数之和.md
+++ b/problems/0015.三数之和.md
@@ -354,6 +354,47 @@ def is_valid(strs)
 end
 ```
 
+php:
+
+```php
+function threeSum(array $nums): array
+{
+    $result = [];
+    $length = count($nums);
+    if ($length < 3) {
+        return [];
+    }
+    sort($nums);
+    for ($i = 0; $i < $length; $i++) {
+        // 如果大于0结束
+        if ($nums[$i] > 0) break;
+        // 去重
+        if ($i > 0 && $nums[$i] == $nums[$i - 1]) continue;
+        $left = $i + 1;
+        $right = $length - 1;
+        // 比较
+        while ($left < $right) {
+            $sum = $nums[$i] + $nums[$left] + $nums[$right];
+           if ($sum < 0) {
+               $left++;
+           } elseif ($sum > 0) {
+               $right--;
+           } else {
+               array_push($result, [$nums[$i], $nums[$left], $nums[$right]]);
+               while ($left < $right && $nums[$left] == $nums[$left + 1]) $left++;
+               while ($left < $right && $nums[$right - 1] == $nums[$right]) $right--;
+               $left++;
+               $right--;
+            }
+        }
+    }
+
+    return $result;
+}
+```
+
+
+
 -----------------------
 * 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)
diff --git a/problems/0501.二叉搜索树中的众数.md b/problems/0501.二叉搜索树中的众数.md
index d2326d67..66be790f 100644
--- a/problems/0501.二叉搜索树中的众数.md
+++ b/problems/0501.二叉搜索树中的众数.md
@@ -345,6 +345,40 @@ public:
 
 Java：
 
+暴力法
+```java
+class Solution {
+	public int[] findMode(FindModeInBinarySearchTree.TreeNode root) {
+		Map<Integer, Integer> map = new HashMap<>();
+		List<Integer> list = new ArrayList<>();
+		if (root == null) return list.stream().mapToInt(Integer::intValue).toArray();
+		// 获得频率 Map
+		searchBST(root, map);
+		List<Map.Entry<Integer, Integer>> mapList = map.entrySet().stream()
+				.sorted((c1, c2) -> c2.getValue().compareTo(c1.getValue()))
+				.collect(Collectors.toList());
+		list.add(mapList.get(0).getKey());
+		// 把频率最高的加入 list
+		for (int i = 1; i < mapList.size(); i++) {
+			if (mapList.get(i).getValue() == mapList.get(i - 1).getValue()) {
+				list.add(mapList.get(i).getKey());
+			} else {
+				break;
+			}
+		}
+		return list.stream().mapToInt(Integer::intValue).toArray();
+	}
+
+	void searchBST(FindModeInBinarySearchTree.TreeNode curr, Map<Integer, Integer> map) {
+		if (curr == null) return;
+		map.put(curr.val, map.getOrDefault(curr.val, 0) + 1);
+		searchBST(curr.left, map);
+		searchBST(curr.right, map);
+	}
+
+}
+```
+
 ```Java
 class Solution {
     ArrayList<Integer> resList;
diff --git a/problems/0701.二叉搜索树中的插入操作.md b/problems/0701.二叉搜索树中的插入操作.md
index 794e0ae2..61027453 100644
--- a/problems/0701.二叉搜索树中的插入操作.md
+++ b/problems/0701.二叉搜索树中的插入操作.md
@@ -271,6 +271,9 @@ class Solution:
 
 
 Go：
+
+递归法
+
 ```Go
 func insertIntoBST(root *TreeNode, val int) *TreeNode {
     if root == nil {
@@ -285,6 +288,31 @@ func insertIntoBST(root *TreeNode, val int) *TreeNode {
     return root
 }
 ```
+迭代法
+```go
+func insertIntoBST(root *TreeNode, val int) *TreeNode {
+    if root == nil {
+        return &TreeNode{Val:val}
+    }
+    node := root
+    var pnode *TreeNode
+    for node != nil {
+        if val > node.Val {
+            pnode = node
+            node = node.Right
+        } else {
+            pnode = node
+            node = node.Left
+        }
+    }
+    if val > pnode.Val {
+        pnode.Right = &TreeNode{Val: val}
+    } else {
+        pnode.Left = &TreeNode{Val: val}
+    }
+    return root
+}
+```
 
 JavaScript版本
 
diff --git a/problems/动态规划-股票问题总结篇.md b/problems/动态规划-股票问题总结篇.md
index cac77b65..d22132c0 100644
--- a/problems/动态规划-股票问题总结篇.md
+++ b/problems/动态规划-股票问题总结篇.md
@@ -381,6 +381,12 @@ dp[i][1] = max(dp[i - 1][1], dp[i - 1][3]);
 dp[i][2] = dp[i - 1][0] + prices[i];
 dp[i][3] = dp[i - 1][2];
 ```
+```C++
+dp[i][0] = max(dp[i - 1][0], max(dp[i - 1][3]- prices[i], dp[i - 1][1]) - prices[i];
+dp[i][1] = max(dp[i - 1][1], dp[i - 1][3]);
+dp[i][2] = dp[i - 1][0] + prices[i];
+dp[i][3] = dp[i - 1][2];
+```
 
 整体代码如下：