diff --git a/asteroid_collision.cpp b/asteroid_collision.cpp
new file mode 100644
index 00000000..da751761
--- /dev/null
+++ b/asteroid_collision.cpp
@@ -0,0 +1,25 @@
+class Solution {
+public:
+    vector<int> asteroidCollision(vector<int>& asteroids) {
+        vector<int> ans;
+        int n=asteroids.size();
+        for(int i=0;i<n;i++){
+            int curr=asteroids[i];
+            if(ans.empty() || curr>0 ){
+                ans.push_back(curr);
+            }
+            else{
+                while(!ans.empty() && ans.back()>0 && ans.back()<abs(curr)){
+                    ans.pop_back();
+                }
+               if(!ans.empty() && ans.back()+curr==0){
+                   ans.pop_back();
+               }
+               else if(ans.empty() || ans.back()<0){
+                   ans.push_back(curr);
+               }
+            }  
+        }
+        return ans;
+    }
+};
diff --git a/balanced_parenthesis.cpp b/balanced_parenthesis.cpp
new file mode 100644
index 00000000..118d942e
--- /dev/null
+++ b/balanced_parenthesis.cpp
@@ -0,0 +1,68 @@
+#include<bits/stdc++.h>
+using namespace std;
+
+bool isValid(string s)
+{
+    int n = s.size();
+    stack<char> st;
+    bool ans = true;
+    for (int i = 0; i < n; i++)
+    {
+        if (s[i] == '{' or s[i] == '(' or s[i] == '[')
+        {
+            st.push(s[i]);
+        }
+        else if (s[i] == ')')
+        {
+            if (!st.empty() and st.top() == '(')
+            {
+                st.pop();
+            }
+            else
+            {
+                ans = false;
+                break;
+            }
+        }
+        else if (s[i] == ']')
+        {
+            if (!st.empty() and st.top() == '[')
+            {
+                st.pop();
+            }
+            else
+            {
+                ans = false;
+                break;
+            }
+        }
+        else if (s[i] == '}')
+        {
+            if (!st.empty() and st.top() == '{')
+            {
+                st.pop();
+            }
+            else
+            {
+                ans = false;
+                break;
+            }
+        }
+    }
+    if(!st.empty()){
+    return false;
+    }
+    return ans;
+}
+int main()
+{
+    string s = "{([])}";
+
+    if(isValid(s)){
+        cout<<"valid string ";
+    }
+    else{
+        cout<<"invalid string ";
+    }
+    return 0;
+}