P1939 【模板】矩阵加速（数列）

https://www.luogu.com.cn/record/75060251

Luogu/P1939/P1939.cpp

@@ -0,0 +1,85 @@
+#include <cstring>
+#include <iostream>
+
+using std::cin;
+using std::cout;
+const char endl = '\n';
+
+const int N = 10;
+const int mod = 1e9 + 7;
+
+class Matrix {
+  private:
+    int data[N][N];
+
+  public:
+    Matrix() {
+        memset(data, 0x00, sizeof(data));
+    }
+
+    int* operator[](int i) {
+        return data[i];
+    }
+
+    void build() {
+        int n = 3;
+
+        for (int i = 1; i <= n; i++) {
+            data[i][i] = 1;
+        }
+    }
+
+    Matrix operator*(Matrix b) const {
+        Matrix c;
+
+        int n = 3;
+
+        for (int i = 1; i <= n; i++) {
+            for (int j = 1; j <= n; j++) {
+                for (int k = 1; k <= n; k++) {
+                    c[i][j] = (c[i][j] + 1ll * data[i][k] * b[k][j] % mod) % mod;
+                }
+            }
+        }
+
+        return c;
+    }
+};
+
+Matrix binpow(Matrix a, int k) {
+    Matrix res;
+    res.build();
+
+    while (k) {
+        if (k & 1) res = res * a;
+        a = a * a;
+        k >>= 1;
+    }
+
+    return res;
+}
+
+int t, n;
+
+int main() {
+    std::ios::sync_with_stdio(false);
+
+    cin >> t;
+
+    Matrix base, pow;
+
+    base[1][1] = 1;
+    base[2][1] = 1;
+    base[3][1] = 1;
+
+    pow[1][1] = 1, pow[1][2] = 0, pow[1][3] = 1;
+    pow[2][1] = 1, pow[2][2] = 0, pow[2][3] = 0;
+    pow[3][1] = 0, pow[3][2] = 1, pow[3][3] = 0;
+
+    while (t--) {
+        cin >> n;
+        cout << (base * binpow(pow, n - 1))[1][1] << endl;
+    }
+
+    return 0;
+}