diff --git a/08_String/Problems/Easy/884_Uncommon_Words_from_Two_Sentences.cpp b/08_String/Problems/Easy/884_Uncommon_Words_from_Two_Sentences.cpp
new file mode 100644
index 0000000..22534be
--- /dev/null
+++ b/08_String/Problems/Easy/884_Uncommon_Words_from_Two_Sentences.cpp
@@ -0,0 +1,56 @@
+/*
+884. Uncommon Words from Two Sentences
+A sentence is a string of single-space separated words where each word consists only of lowercase letters.
+A word is uncommon if it appears exactly once in one of the sentences, and does not appear in the other sentence.
+Given two sentences s1 and s2, return a list of all the uncommon words. You may return the answer in any order.
+Example 1:
+Input: s1 = "this apple is sweet", s2 = "this apple is sour"
+Output: ["sweet","sour"]
+Explanation:
+The word "sweet" appears only in s1, while the word "sour" appears only in s2.
+Example 2:
+Input: s1 = "apple apple", s2 = "banana"
+Output: ["banana"]
+Constraints:
+1 <= s1.length, s2.length <= 200
+s1 and s2 consist of lowercase English letters and spaces.
+s1 and s2 do not have leading or trailing spaces.
+All the words in s1 and s2 are separated by a single space.
+*/
+class Solution {
+public:
+    vector<string> uncommonFromSentences(string s1, string s2) {
+        vector<string> ans;
+         map<string,int> map1,map2;
+        string str = "";
+        for(char ch:s1){
+            if(ch!=' ') str+=ch;
+            else{ 
+             map1[str]++;
+             str="";
+             }    
+        }
+        map1[str]++;
+        str="";
+
+         for(char ch:s2){
+            if(ch!=' ') str+=ch;
+            else{ 
+            map2[str]++;
+             str="";
+             }    
+        }
+        map2[str]++;
+        str="";
+
+    for(auto i:map2){
+        string sen = i.first;
+        int n1 = i.second;
+        if(map1[sen]) map1[sen] += n1;
+        else map1[sen]= n1;
+    }
+    for(auto i:map1) if(i.second==1) ans.push_back(i.first);
+    // for(auto i:map1)ans.push_back(i.first);
+    return ans;
+    }
+};
\ No newline at end of file
diff --git a/08_String/Problems/Hard/Longest_valid_Parentheses.cpp b/08_String/Problems/Hard/Longest_valid_Parentheses.cpp
new file mode 100644
index 0000000..b7bf22f
--- /dev/null
+++ b/08_String/Problems/Hard/Longest_valid_Parentheses.cpp
@@ -0,0 +1,50 @@
+/*
+Longest valid Parentheses
+Given a string str consisting of opening and closing parenthesis '(' and ')'. Find length of the longest valid parenthesis substring.
+A parenthesis string is valid if:
+For every opening parenthesis, there is a closing parenthesis.
+Opening parenthesis must be closed in the correct order.
+Examples :
+Input: str = ((()
+Output: 2
+Explaination: The longest valid parenthesis substring is "()".
+Input: str = )()())
+Output: 4
+Explaination: The longest valid parenthesis substring is "()()".
+Expected Time Complexity: O(|str|)
+Expected Auxiliary Space: O(|str|)
+Constraints:
+1 ≤ |str| ≤ 105  
+*/
+// User function Template for C++
+
+class Solution {
+  public:
+    int maxLength(string& str) {
+        // code here
+         int n = str.size();
+        stack<int> st;
+        int ans = 0;
+        for(int i=0; i<n; i++)
+        {
+            if(str[i] == '(')
+            {
+                st.push(i);
+            }
+            else
+            {
+                if(!st.empty() && str[st.top()] == '(')
+                {
+                    st.pop();
+                    int first = st.empty() ? -1 : st.top();
+                    ans = max(ans,i-first);
+                }
+                else 
+                {
+                    st.push(i);
+                }
+            }
+        }
+        return ans;
+    }
+};
\ No newline at end of file
diff --git a/08_String/Problems/Medium/539_Minimum_Time_Difference.cpp b/08_String/Problems/Medium/539_Minimum_Time_Difference.cpp
new file mode 100644
index 0000000..79f93d6
--- /dev/null
+++ b/08_String/Problems/Medium/539_Minimum_Time_Difference.cpp
@@ -0,0 +1,40 @@
+/*
+539. Minimum Time Difference
+Given a list of 24-hour clock time points in "HH:MM" format, return the minimum minutes difference between any two time-points in the list.
+Example 1:
+Input: timePoints = ["23:59","00:00"]
+Output: 1
+Example 2:
+Input: timePoints = ["00:00","23:59","00:00"]
+Output: 0
+Constraints:
+2 <= timePoints.length <= 2 * 104
+timePoints[i] is in the format "HH:MM".
+*/
+class Solution {
+public:
+    int findMinDifference(vector<string>& timePoints) {
+        vector<int> minutes(timePoints.size());
+        
+        // Convert times to minutes
+        for (int i = 0; i < timePoints.size(); ++i) {
+            int h = stoi(timePoints[i].substr(0, 2));
+            int m = stoi(timePoints[i].substr(3));
+            minutes[i] = h * 60 + m;
+        }
+
+        // Sort times in ascending order
+        sort(minutes.begin(), minutes.end());
+
+        // Find minimum difference across adjacent elements
+        int minDiff = INT_MAX;
+        for (int i = 0; i < minutes.size() - 1; ++i) {
+            minDiff = min(minDiff, minutes[i + 1] - minutes[i]);
+        }
+
+        // Consider the circular difference between last and first element
+        minDiff = min(minDiff, 24 * 60 - minutes.back() + minutes.front());
+
+        return minDiff;
+    }
+};
\ No newline at end of file
diff --git a/13_Stack/Problems/Hard/Longest_valid_Parentheses.cpp b/13_Stack/Problems/Hard/Longest_valid_Parentheses.cpp
new file mode 100644
index 0000000..b7bf22f
--- /dev/null
+++ b/13_Stack/Problems/Hard/Longest_valid_Parentheses.cpp
@@ -0,0 +1,50 @@
+/*
+Longest valid Parentheses
+Given a string str consisting of opening and closing parenthesis '(' and ')'. Find length of the longest valid parenthesis substring.
+A parenthesis string is valid if:
+For every opening parenthesis, there is a closing parenthesis.
+Opening parenthesis must be closed in the correct order.
+Examples :
+Input: str = ((()
+Output: 2
+Explaination: The longest valid parenthesis substring is "()".
+Input: str = )()())
+Output: 4
+Explaination: The longest valid parenthesis substring is "()()".
+Expected Time Complexity: O(|str|)
+Expected Auxiliary Space: O(|str|)
+Constraints:
+1 ≤ |str| ≤ 105  
+*/
+// User function Template for C++
+
+class Solution {
+  public:
+    int maxLength(string& str) {
+        // code here
+         int n = str.size();
+        stack<int> st;
+        int ans = 0;
+        for(int i=0; i<n; i++)
+        {
+            if(str[i] == '(')
+            {
+                st.push(i);
+            }
+            else
+            {
+                if(!st.empty() && str[st.top()] == '(')
+                {
+                    st.pop();
+                    int first = st.empty() ? -1 : st.top();
+                    ans = max(ans,i-first);
+                }
+                else 
+                {
+                    st.push(i);
+                }
+            }
+        }
+        return ans;
+    }
+};
\ No newline at end of file
diff --git a/18_Greedy/Problems/Medium/Minimize_the_Heights_II.cpp b/18_Greedy/Problems/Medium/Minimize_the_Heights_II.cpp
new file mode 100644
index 0000000..bddf028
--- /dev/null
+++ b/18_Greedy/Problems/Medium/Minimize_the_Heights_II.cpp
@@ -0,0 +1,41 @@
+/*
+Minimize the Heights II
+Given an array arr[] denoting heights of N towers and a positive integer K.
+For each tower, you must perform exactly one of the following operations exactly once.
+Increase the height of the tower by K
+Decrease the height of the tower by K
+Find out the minimum possible difference between the height of the shortest and tallest towers after you have modified each tower.
+You can find a slight modification of the problem here.
+Note: It is compulsory to increase or decrease the height by K for each tower. After the operation, the resultant array should not contain any negative integers.
+Examples :
+Input: k = 2, arr[] = {1, 5, 8, 10}
+Output: 5
+Explanation: The array can be modified as {1+k, 5-k, 8-k, 10-k} = {3, 3, 6, 8}.The difference between the largest and the smallest is 8-3 = 5.
+Input: k = 3, arr[] = {3, 9, 12, 16, 20}
+Output: 11
+Explanation: The array can be modified as {3+k, 9+k, 12-k, 16-k, 20-k} -> {6, 12, 9, 13, 17}.The difference between the largest and the smallest is 17-6 = 11. 
+Expected Time Complexity: O(n*logn)
+Expected Auxiliary Space: O(n)
+Constraints
+1 ≤ k ≤ 107
+1 ≤ n ≤ 105
+1 ≤ arr[i] ≤ 107
+*/
+// User function template for C++
+
+class Solution {
+  public:
+    int getMinDiff(vector<int> &arr, int k) {
+        // code here
+        int n = arr.size();
+        sort(arr.begin(),arr.end());
+        int min_diff = arr[n-1] - arr[0];
+        for(int i = 1; i < n; i++){
+            if(arr[i] < k) continue;
+            int mini = min(arr[0] + k, arr[i] - k);
+            int maxi = max(arr[n-1] - k, arr[i-1] + k);
+            min_diff = min(min_diff, maxi - mini);
+        }
+        return min_diff;
+    }
+};
\ No newline at end of file
diff --git a/25_Dynamic_Programming/Problems_on_dp/Hard/Longest_valid_Parentheses.cpp b/25_Dynamic_Programming/Problems_on_dp/Hard/Longest_valid_Parentheses.cpp
new file mode 100644
index 0000000..b7bf22f
--- /dev/null
+++ b/25_Dynamic_Programming/Problems_on_dp/Hard/Longest_valid_Parentheses.cpp
@@ -0,0 +1,50 @@
+/*
+Longest valid Parentheses
+Given a string str consisting of opening and closing parenthesis '(' and ')'. Find length of the longest valid parenthesis substring.
+A parenthesis string is valid if:
+For every opening parenthesis, there is a closing parenthesis.
+Opening parenthesis must be closed in the correct order.
+Examples :
+Input: str = ((()
+Output: 2
+Explaination: The longest valid parenthesis substring is "()".
+Input: str = )()())
+Output: 4
+Explaination: The longest valid parenthesis substring is "()()".
+Expected Time Complexity: O(|str|)
+Expected Auxiliary Space: O(|str|)
+Constraints:
+1 ≤ |str| ≤ 105  
+*/
+// User function Template for C++
+
+class Solution {
+  public:
+    int maxLength(string& str) {
+        // code here
+         int n = str.size();
+        stack<int> st;
+        int ans = 0;
+        for(int i=0; i<n; i++)
+        {
+            if(str[i] == '(')
+            {
+                st.push(i);
+            }
+            else
+            {
+                if(!st.empty() && str[st.top()] == '(')
+                {
+                    st.pop();
+                    int first = st.empty() ? -1 : st.top();
+                    ans = max(ans,i-first);
+                }
+                else 
+                {
+                    st.push(i);
+                }
+            }
+        }
+        return ans;
+    }
+};
\ No newline at end of file
diff --git a/GFG/HARD/Longest_valid_Parentheses.cpp b/GFG/HARD/Longest_valid_Parentheses.cpp
new file mode 100644
index 0000000..b7bf22f
--- /dev/null
+++ b/GFG/HARD/Longest_valid_Parentheses.cpp
@@ -0,0 +1,50 @@
+/*
+Longest valid Parentheses
+Given a string str consisting of opening and closing parenthesis '(' and ')'. Find length of the longest valid parenthesis substring.
+A parenthesis string is valid if:
+For every opening parenthesis, there is a closing parenthesis.
+Opening parenthesis must be closed in the correct order.
+Examples :
+Input: str = ((()
+Output: 2
+Explaination: The longest valid parenthesis substring is "()".
+Input: str = )()())
+Output: 4
+Explaination: The longest valid parenthesis substring is "()()".
+Expected Time Complexity: O(|str|)
+Expected Auxiliary Space: O(|str|)
+Constraints:
+1 ≤ |str| ≤ 105  
+*/
+// User function Template for C++
+
+class Solution {
+  public:
+    int maxLength(string& str) {
+        // code here
+         int n = str.size();
+        stack<int> st;
+        int ans = 0;
+        for(int i=0; i<n; i++)
+        {
+            if(str[i] == '(')
+            {
+                st.push(i);
+            }
+            else
+            {
+                if(!st.empty() && str[st.top()] == '(')
+                {
+                    st.pop();
+                    int first = st.empty() ? -1 : st.top();
+                    ans = max(ans,i-first);
+                }
+                else 
+                {
+                    st.push(i);
+                }
+            }
+        }
+        return ans;
+    }
+};
\ No newline at end of file
diff --git a/GFG/Medium Problems/Minimize_the_Heights_II.cpp b/GFG/Medium Problems/Minimize_the_Heights_II.cpp
new file mode 100644
index 0000000..bddf028
--- /dev/null
+++ b/GFG/Medium Problems/Minimize_the_Heights_II.cpp	
@@ -0,0 +1,41 @@
+/*
+Minimize the Heights II
+Given an array arr[] denoting heights of N towers and a positive integer K.
+For each tower, you must perform exactly one of the following operations exactly once.
+Increase the height of the tower by K
+Decrease the height of the tower by K
+Find out the minimum possible difference between the height of the shortest and tallest towers after you have modified each tower.
+You can find a slight modification of the problem here.
+Note: It is compulsory to increase or decrease the height by K for each tower. After the operation, the resultant array should not contain any negative integers.
+Examples :
+Input: k = 2, arr[] = {1, 5, 8, 10}
+Output: 5
+Explanation: The array can be modified as {1+k, 5-k, 8-k, 10-k} = {3, 3, 6, 8}.The difference between the largest and the smallest is 8-3 = 5.
+Input: k = 3, arr[] = {3, 9, 12, 16, 20}
+Output: 11
+Explanation: The array can be modified as {3+k, 9+k, 12-k, 16-k, 20-k} -> {6, 12, 9, 13, 17}.The difference between the largest and the smallest is 17-6 = 11. 
+Expected Time Complexity: O(n*logn)
+Expected Auxiliary Space: O(n)
+Constraints
+1 ≤ k ≤ 107
+1 ≤ n ≤ 105
+1 ≤ arr[i] ≤ 107
+*/
+// User function template for C++
+
+class Solution {
+  public:
+    int getMinDiff(vector<int> &arr, int k) {
+        // code here
+        int n = arr.size();
+        sort(arr.begin(),arr.end());
+        int min_diff = arr[n-1] - arr[0];
+        for(int i = 1; i < n; i++){
+            if(arr[i] < k) continue;
+            int mini = min(arr[0] + k, arr[i] - k);
+            int maxi = max(arr[n-1] - k, arr[i-1] + k);
+            min_diff = min(min_diff, maxi - mini);
+        }
+        return min_diff;
+    }
+};
\ No newline at end of file
diff --git a/Leet Code Problems/Easy/884_Uncommon_Words_from_Two_Sentences.cpp b/Leet Code Problems/Easy/884_Uncommon_Words_from_Two_Sentences.cpp
new file mode 100644
index 0000000..22534be
--- /dev/null
+++ b/Leet Code Problems/Easy/884_Uncommon_Words_from_Two_Sentences.cpp	
@@ -0,0 +1,56 @@
+/*
+884. Uncommon Words from Two Sentences
+A sentence is a string of single-space separated words where each word consists only of lowercase letters.
+A word is uncommon if it appears exactly once in one of the sentences, and does not appear in the other sentence.
+Given two sentences s1 and s2, return a list of all the uncommon words. You may return the answer in any order.
+Example 1:
+Input: s1 = "this apple is sweet", s2 = "this apple is sour"
+Output: ["sweet","sour"]
+Explanation:
+The word "sweet" appears only in s1, while the word "sour" appears only in s2.
+Example 2:
+Input: s1 = "apple apple", s2 = "banana"
+Output: ["banana"]
+Constraints:
+1 <= s1.length, s2.length <= 200
+s1 and s2 consist of lowercase English letters and spaces.
+s1 and s2 do not have leading or trailing spaces.
+All the words in s1 and s2 are separated by a single space.
+*/
+class Solution {
+public:
+    vector<string> uncommonFromSentences(string s1, string s2) {
+        vector<string> ans;
+         map<string,int> map1,map2;
+        string str = "";
+        for(char ch:s1){
+            if(ch!=' ') str+=ch;
+            else{ 
+             map1[str]++;
+             str="";
+             }    
+        }
+        map1[str]++;
+        str="";
+
+         for(char ch:s2){
+            if(ch!=' ') str+=ch;
+            else{ 
+            map2[str]++;
+             str="";
+             }    
+        }
+        map2[str]++;
+        str="";
+
+    for(auto i:map2){
+        string sen = i.first;
+        int n1 = i.second;
+        if(map1[sen]) map1[sen] += n1;
+        else map1[sen]= n1;
+    }
+    for(auto i:map1) if(i.second==1) ans.push_back(i.first);
+    // for(auto i:map1)ans.push_back(i.first);
+    return ans;
+    }
+};
\ No newline at end of file
diff --git a/Leet Code Problems/Medium/539_Minimum_Time_Difference.cpp b/Leet Code Problems/Medium/539_Minimum_Time_Difference.cpp
new file mode 100644
index 0000000..79f93d6
--- /dev/null
+++ b/Leet Code Problems/Medium/539_Minimum_Time_Difference.cpp	
@@ -0,0 +1,40 @@
+/*
+539. Minimum Time Difference
+Given a list of 24-hour clock time points in "HH:MM" format, return the minimum minutes difference between any two time-points in the list.
+Example 1:
+Input: timePoints = ["23:59","00:00"]
+Output: 1
+Example 2:
+Input: timePoints = ["00:00","23:59","00:00"]
+Output: 0
+Constraints:
+2 <= timePoints.length <= 2 * 104
+timePoints[i] is in the format "HH:MM".
+*/
+class Solution {
+public:
+    int findMinDifference(vector<string>& timePoints) {
+        vector<int> minutes(timePoints.size());
+        
+        // Convert times to minutes
+        for (int i = 0; i < timePoints.size(); ++i) {
+            int h = stoi(timePoints[i].substr(0, 2));
+            int m = stoi(timePoints[i].substr(3));
+            minutes[i] = h * 60 + m;
+        }
+
+        // Sort times in ascending order
+        sort(minutes.begin(), minutes.end());
+
+        // Find minimum difference across adjacent elements
+        int minDiff = INT_MAX;
+        for (int i = 0; i < minutes.size() - 1; ++i) {
+            minDiff = min(minDiff, minutes[i + 1] - minutes[i]);
+        }
+
+        // Consider the circular difference between last and first element
+        minDiff = min(minDiff, 24 * 60 - minutes.back() + minutes.front());
+
+        return minDiff;
+    }
+};
\ No newline at end of file