update

src/U206625/U206625_video.cpp

@@ -0,0 +1,24 @@
+#include <iostream>
+#include <string>
+
+using std::cin, std::cout, std::string;
+using ull = unsigned long long;
+
+constexpr size_t MAX_N {(size_t)3e5+5}, MOD {998244353};
+string s;
+ull left_ok[MAX_N], stk[MAX_N], stk_size, left_index[MAX_N], ans;
+
+int main(){
+    cin>>s;
+
+    for(size_t i {1};i<=s.size();i++){
+        if(s[i-1]=='('){
+            stk[stk_size++] = i;
+        }else if(stk_size>0){
+            left_index[i] = stk[--stk_size];
+            left_ok[i] = (left_ok[left_index[i]-1] + left_index[i]) % MOD;
+            ans = ( ans + left_ok[i] * (s.size() - i + 1)) % MOD;
+        }
+    }
+    cout<<ans<<'\n';
+}