diff --git a/1048-longest-string-chain/1048-longest-string-chain.cpp b/1048-longest-string-chain/1048-longest-string-chain.cpp
new file mode 100644
index 00000000..238b6231
--- /dev/null
+++ b/1048-longest-string-chain/1048-longest-string-chain.cpp
@@ -0,0 +1,22 @@
+bool cmp(string &a, string &b){
+    return a.length() < b.length();
+}
+class Solution {
+public:
+    int longestStrChain(vector<string>& words) {
+        sort(words.begin(), words.end(), cmp);
+        map<string, int> mp;
+        int ans = 0;
+        for(auto word: words){
+            int cur = 0;
+            for(int i=0;i<word.length(); i++){
+                string prev = word.substr(0,i)+word.substr(i+1);
+                cur = max(cur, mp[prev]+1);
+            }
+            mp[word] = cur;
+            ans = max(ans, cur);
+        }
+
+        return ans;
+    }
+};
\ No newline at end of file
diff --git a/Dynamic Programming/buy_and_sell_stock_iv.cpp b/Dynamic Programming/buy_and_sell_stock_iv.cpp
new file mode 100644
index 00000000..0c62dd38
--- /dev/null
+++ b/Dynamic Programming/buy_and_sell_stock_iv.cpp	
@@ -0,0 +1,18 @@
+class Solution {
+public:
+    int maxProfit(int k, vector<int>& prices) {
+
+        int n = prices.size();
+        vector<int> profit_after_buying(k + 1, -1e9), profit_after_selling(k + 1, 0);
+
+        for (int i = 0; i < prices.size(); ++i) {
+            int cur_price = prices[i]; 
+            for (int j = k; j >= 1; --j) {
+                profit_after_buying[j] = max(profit_after_buying[j], profit_after_selling[j-1] - cur_price);
+                profit_after_selling[j] = max(profit_after_selling[j], profit_after_buying[j] + cur_price);
+            }
+        }
+        return profit_after_selling[k];
+    }
+
+};
\ No newline at end of file