new file: CF2205E.cpp

CF2205E.cpp

@@ -0,0 +1,36 @@
+#include <bits/stdc++.h>
+using namespace std;
+const int mod = 998244353;
+int t, n, a[8005], nxt[8005];
+long long f[8005];
+int main() {
+    scanf("%d", &t);
+    while (t--) {
+        scanf("%d", &n);
+        for (int i = 1; i <= n; i++)
+            scanf("%d", &a[i]);
+        f[0] = 1;
+        for (int i = 1; i <= n; i++) {
+            int k = i + 1;
+            for (int j = 0; j <= i; j++)
+                nxt[j] = i + 1;
+            for (int j = i - 1; j >= 1; j--) {
+                while (k != i + 1 && a[k - 1] != a[j])
+                    k = nxt[k];
+                if (a[k - 1] == a[j])
+                    k--;
+                nxt[j] = k;
+            }
+            for (int j = i - 1; j >= 0; j--)
+                if (nxt[j + 1] == i + 1)
+                    f[i] = (f[i] + f[j]) % mod;
+        }
+        printf("%lld\n", f[n]);
+        memset(f, 0, sizeof(f[0]) * (n + 1));
+    }
+    return 0;
+}
+/*
+KMP
+ABA.rev = A.rev + B.rev + A.rev
+*/