Create F.cpp

Author: SmitMangukiya

Codeforces_Contests/7_Round_674_Div_3/F.cpp

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+#include<bits/stdc++.h>
+using namespace std;
+
+#define int long long
+#define ll long long
+#define pb push_back
+#define mp make_pair
+#define f(i,a,n) for(int i=a ; i<n ; i++)
+#define rf(i,n,a) for(int i=n ; i>=a ; i--)
+#define F first
+#define S second
+#define all(c) (c).begin(),(c).end()
+#define sz(v) (int)(v).size()
+#define fast ios::sync_with_stdio(0); cin.tie(0); cout.tie(0)
+
+typedef long double ld;
+typedef vector<int> vi;
+typedef pair<int, int> pii;
+typedef pair<pii, int> ppi;
+typedef vector<pii> vpi;
+
+const int inf = 1e9;
+const int inf64 = 1e18;
+const int MOD = inf + 7;
+
+int32_t main() {
+   fast;
+   int n;
+   cin >> n;
+
+   string s;
+   cin >> s;
+
+   vector<vector<int>> dp(n + 1, vector<int>(3, 0));
+
+   int cur = 1;
+
+   for (int i = 1 ; i <= n ; i++) {
+      if (s[i - 1] == 'a' || s[i - 1] == '?') {
+         dp[i][0] = dp[i - 1][0] + cur;
+         dp[i][1] = dp[i - 1][1];
+         dp[i][2] = dp[i - 1][2];
+      }
+      if (s[i - 1] == 'b' || s[i - 1] == '?') {
+         dp[i][0] += dp[i - 1][0];
+         dp[i][1] += dp[i - 1][1] + dp[i - 1][0];
+         dp[i][2] += dp[i - 1][2];
+      }
+      if (s[i - 1] == 'c' || s[i - 1] == '?') {
+         dp[i][0] += dp[i - 1][0];
+         dp[i][1] += dp[i - 1][1];
+         dp[i][2] += dp[i - 1][2] + dp[i - 1][1];
+      }
+      if (s[i - 1] == '?') {
+         cur = (cur * 3) % MOD;
+      }
+      dp[i][0] %= MOD;
+      dp[i][1] %= MOD;
+      dp[i][2] %= MOD;
+   }
+   cout << dp[n][2] << "\n";
+}