Day 4 Solution 1

Author: Apoorv012

Problems/Data-structures/Day-04/sol/Apoorv012/Solution1.cpp

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+/*
+
+We have to find the minimum cost that we could acheive by placing ( and ) in the blank spaces. We have to make sure that () are valid.
+
+I saw the pattern, that we can set the blank to ) as long as there is atleast one open (.
+
+Time: O(n);
+Space: O(n);
+
+Submission Link: https://codeforces.com/contest/1997/submission/355679346
+
+*/
+
+#include <bits/stdc++.h>
+using namespace std;
+
+using ll = long long;
+
+void solve() {
+    ll n;
+    cin >> n;
+    string s;
+    cin >> s;
+
+    // cout << "n, s: " << n << " " << s << endl;
+
+    ll ans = 0;
+    stack<ll> st;
+    for (ll i = 0; i < n; i++) {
+        if (s[i] == '(') {
+            st.push(i);
+            // cout << i << " pushed (\n";
+        }
+        else if (s[i] == ')') {
+            if (st.empty()) {
+                cout << -1 << endl;
+                return;
+            }
+            ll start = st.top();
+            st.pop();
+            ans += i - start;
+            // cout << i << " poped )\n";
+        }
+        else {
+            if (st.empty()) {
+                st.push(i);
+                // cout << i << " pushed _\n";
+            }
+            else {
+                ll start = st.top();
+                st.pop();
+                ans += i - start;
+                // cout << i << " popped _\n";
+            }
+        }
+    }
+
+    cout << ans << endl;
+}
+
+int main() {
+    int t;
+    cin >> t;
+    while (t--) {
+        solve();
+        // cout << t << " done\n";
+    }
+}