q001 of day 4 solved

Author: DoonMad

Problems/Data-structures/Day-04/sol/DoonMad/q001.cpp

@@ -0,0 +1,36 @@
+#include<bits/stdc++.h>
+
+using namespace std;
+
+void solve(){
+    int n; cin>>n;
+    string s; cin>>s;
+    stack<int> st;
+    long long res=0;
+    
+    st.push(0); // inserting first element (always a '(')
+    for(int i=1; i<n; i++){
+        // trying to close a pair immediately to minimize distance (greedy)
+        if(s[i] == ')' || (s[i] == '_' && !st.empty())){
+            res += (i-st.top());
+            st.pop();
+        }
+        else{
+            st.push(i);
+        }
+    }
+
+    cout<<res<<endl;
+}
+
+// Time Complexity: O(N)
+// Space Complexity: O(N) (string + stack)
+
+int main(int argc, char const *argv[])
+{
+    int t; cin>>t;
+    while(t--){
+        solve();
+    }
+    return 0;
+}