new: CSES String Algorithms problems

solutions/CSES/String Algorithms/1731 - Word Combinations.cpp

@@ -0,0 +1,71 @@
+#include <bits/stdc++.h>
+using namespace std;
+
+const int mod = 1e9 + 7;
+
+struct T {
+   struct node {
+      int next[26];
+      bool terminal;
+      node() {
+         for (int i = 0; i < 26; i++) next[i] = -1;
+         terminal = false;
+      }
+   };
+   vector<node> st;
+
+   T() { st.emplace_back(); }
+
+   void insert(string &s) {
+      int n = s.length();
+      int cur = 0;
+      for (int i = 0; i < n; i++)
+         if (st[cur].next[s[i] - 'a'] == -1) {
+            st[cur].next[s[i] - 'a'] = st.size();
+            cur = st.size();
+            st.emplace_back();
+         } else
+            cur = st[cur].next[s[i] - 'a'];
+      st[cur].terminal = true;
+   }
+
+   int search(string &s) {
+      int n = s.length();
+      vector<int> dp(n + 1);
+      dp[0] = 1;
+      for (int len = 1; len <= n; len++) {
+         int cur = 0;
+         for (int i = n - len; i < n; i++) {
+            if (st[cur].next[s[i] - 'a'] == -1) break;
+            cur = st[cur].next[s[i] - 'a'];
+            if (st[cur].terminal) dp[len] = (dp[len] + dp[n - (i + 1)]) % mod;
+         }
+      }
+      return dp[n];
+   }
+};
+
+void solve() {
+   string s;
+   cin >> s;
+   int k;
+   cin >> k;
+   T t;
+   while (k--) {
+      string x;
+      cin >> x;
+      t.insert(x);
+   }
+
+   cout << t.search(s) << "\n";
+}
+
+int main() {
+   ios::sync_with_stdio(false);
+   cin.tie(0);
+   cout.tie(0);
+
+   int t = 1;
+   // cin >> t;
+   while (t--) solve();
+}